1 GROUND ENGAGING TOOLS This invention relates to ground engaging tools for earthmoving and mining equipment. The invention has particular application to ground engaging tools of the type commonly known as lip shrouds and wear plates for the cutting edge of excavator buckets 5 and similar earthmoving devices. Accordingly the invention will be described with particular reference to such application. However, the invention may have application to other types of ground engaging tools and in particular to other lip shrouds and wear plates for other equipment for example, shovel buckets, loader buckets, dragline buckets, bulldozer blades, drott grabs, bobcat buckets and grabs, and backhoes. 0 Typically, excavator buckets and the like have a base or floor with a cutting edge or lip to which ground engaging tools are fitted to engage the ground or spoil which is to be excavated or loaded as the case may be for improved digging efficiency and to protect the lip from wear. Commonly, the cutting teeth are fitted to respective noses or nose mounts which are fixed in a permanent or semi-permanent manner to the base of the bucket by weld and 5 protrude forward from the lip. In some types of equipment an adaptor is mounted to each nose mount and the tooth is fitted to the adaptor. The nose mounts are normally fitted to the cutting edge or lip in spaced apart relationship with the intervening teeth also spaced so as to efficiently cut the ground or spoil to be removed. Consequently, the portions of the lip between the spaced apart nose mounts 0 also dig to some extent and in any event are exposed to the abrasive effects of spoil flowing across the upper face thereof and at the same time the lower face suffers the abrasive effects of sliding across the uncut ground. While the lip itself may be a semi-permanent wear plate which is welded to the bucket floor, replacement from time to time can require a substantial time consuming operation. Consequently, in order to extend the life of a lip or lip plate, lip Z5 shrouds are often fitted between the nose mounts and welded to the floor adjacent the lip. Replacement of such lip shrouds typically requires them to be cut from the floor and that can be a fairly long and arduous task resulting in significant machine downtime. The present invention is aimed at providing alternative lip shrouds and associated components which allow the lip shrouds to be removed and replaced in an easier and quicker 30 operation. With the foregoing in view, the invention resides broadly in the combination of a lip shroud and retainer for operatively securing the lip shroud to the lip of a bucket, blade or the like, the lip shroud having a cutting tip at its front and a mounting portion rearward of said cutting tip, said mounting portion including spaced apart upper and lower jaw members, each 2 said jaw member having an inner face and an outer face and at least one of said jaw members having a passage therethrough opening at one end to the inner face and at the other end to the outer face, the retainer being adapted to fit in said passage and said at least one jaw member being arranged to engage with said retainer in the operative position so as to prevent the 5 retainer passing through said passage from the outer face to the inner face. In another aspect, the invention resides broadly in the combination of a lip shroud and retainer for operatively securing the lip shroud to the lip of a bucket, blade or the like, the lip shroud having a cutting tip at its front and a mounting portion rearward of said cutting tip, said mounting portion including spaced apart upper and lower jaw members, each said jaw ) member having an inner face and an outer face and at least one of said jaw members having a passage therethrough opening at one end to the inner face and at the other end to the outer face, the passage and the retainer being made and arranged such that the retainer fits in said passage and engages with said retainer in the operative position so as to prevent the retainer passing through said passage from the outer face to the inner face whereby when the lip 5 shroud is fitted to the lip of a bucket the retainer can be fitted in the passage and secured to the lip of the bucket whereby the retainer retains the lip shroud on the lip. Preferably, said at least one jaw member includes stop means which protrudes into said passage to engage said retainer to prevent it passing through said passage. In another aspect, the invention resides broadly in a lip shroud for earthmoving and D mining equipment, the lip shroud having a cutting tip at its front and a mounting portion rearward of said cutting tip, said mounting portion including spaced apart upper and lower jaw members, each said jaw member having an inner face and an outer face and at least one of said jaw members having a passage therethrough opening at one end to the inner face and at the other end to the outer face of said at least one jaw member, said passage being defined Z5 at least in part by a protruding portion of said jaw member adapted to cause a restriction in said passage forming stop means adapted to engage a complementary to prevent it passing through said passage. Preferably, the passage through the lip shroud is defined at least in part by laterally and longitudinally spaced upper and lower faces separated by said stop means. Preferably, 30 such faces are substantially parallel to each other with said upper face being further from the axis of the passage than the lower face. It is also preferred that said stop means be an annular face providing a shoulder against which a complementary annular face of the retainer can engage. In a preferred form, such annular face is substantially orthogonal to the axis of said 3 passage and to said upper and lower faces giving a stepped appearance to the passage when viewed in cross section. In yet another aspect, the invention resides broadly in a retainer including an annular wall with an inner face defining a passage and an outer face defining at least in part a stop portion having a stop face inclined to said inner face. Preferably, said outer face has two laterally and longitudinally spaced face portions spaced outwardly from said inner face and said stop face is annular face contiguous with and between said two laterally and longitudinally spaced face portions. Preferably, said passage and said retainer have complementary shapes adapted to prevent rotation of the retainer within the passage. In a preferred form, the passage is generally obround (that is, cylindrical with opposed flat portions across opposite chords of the passage) and the retainer has a complementary obround shape (with complementary opposed flat lands). In another aspect, the invention resides broadly in the combination of a lip shroud and retainer for operatively securing the lip shroud to the lip of a bucket, blade or the like, the lip shroud having a cutting tip at its front and a mounting portion rearward of said cutting tip, said mounting portion including spaced apart upper and lower jaw members, each said jaw member having an inner face and an outer face and at least one of said jaw members having a passage therethrough opening at one end to the inner face and at the other end to the outer ) face, the retainer being adapted to fit in said passage and said at least one jaw member being adapted to engage with said retainer in the operative position to prevent relative movement therebetween in the forward and rearward direction. In order that the invention may be more clearly understood and put into practice, the invention will now be described with reference to the accompanying drawings wherein: 5 Fig. 1 is pictorial representation of an excavator bucket from the front with a plurality of teeth mounted on complementary nose mounts at the lip of the bucket; Fig. 2 is pictorial representation of the excavator bucket of Fig. 1 from its right side; Fig. 3 is a front elevation of the excavator bucket of Fig. 1; Fig. 4 is pictorial representation of a section of the lip portion of the bucket of Fig. 1 0 with lip shrouds according to the present invention fitted between adjacent teeth; Fig. 5 is a pictorial representation of a portion of the lip of the bucket of Fig. 1 from above showing the lip shroud fitted but without the adjacent nose mounts and teeth; Fig. 6 is a pictorial representation of a portion of the lip of the bucket of Fig. 1 from below showing the lip shroud fitted but without the adjacent nose mounts and teeth; 4 Fig. 7 is a pictorial representation of the lip shroud shown in Fig. 4 without the retainer fitted; Fig. 8 is a sectional pictorial representation of the lip shroud shown in Fig. 4; Fig. 9 is a sectional pictorial representation of the lip shroud shown in Fig. 4 fitted to i the bucket lip; Fig. 10 is a sectional side elevation of the lip shroud shown in Fig. 4 fitted to the bucket lip; Fig. 11 is a pictorial representation of the retainer shown holding the lip shroud to the bucket lip in Figs. 4, 5,6, 9 and 10 from the outside; ) Fig. 12 is a pictorial representation of the retainer shown holding the lip shroud to the bucket lip in Figs. 4, 5,6, 9 and 10 from the inside; Fig. 13 is a sectional pictorial representation of the retainer of Fig. 11 along the short diametral plane; and Fig. 14 is a sectional pictorial representation of the retainer of Fig. 11 along the long 5 diametral plane. The bucket 10 illustrated in Fig. 1 has a floor 11 with a ground engaging leading edge (or lip) 12 at its front. The floor curves upwardly behind the lip to form a contiguous rear wall 13 which in turn curves upwards and forwards to form a contiguous upper wall 14, the floor, the rear wall and the upper wall forming a generally u-shaped bucket enclosed by 3 opposed generally planar side walls 16 and 18 and defining an open front 15. A curved lifting arch or bar 21 extends across the top of the bucket between the side walls and a plurality of spaced apart lifting lugs 19 are welded to the arch and the upper wall for connection of an excavator lifting arm and crowd arm thereto in known manner. A plurality of spaced apart nose mounts 30 are welded to the bucket floor 11 adjacent 5 the lip 12 and extend forward beyond the lip. Teeth 31 are fitted to the nose mounts and secured thereto by pins, wedges or other devices. While not shown in Figs. 1 to 3, the bucket has lip shrouds 41 mounted to the floor over the lip 12 with each lip shroud being secured to the bucket by a top retainer 42 and a bottom retainer 43 which are welded to the bucket floor by fillet welds shown as Items 44 30 and 45 respectively. As can be seen in Fig. 7, the lip shroud has a wedge shaped tip portion 51 with a cutting edge 52 at its front and a mounting portion 53 extending rearwardly from the cutting tip portion. The mounting portion includes spaced apart upper and lower plates 56 and 57 5 with the forward part of the top plate converging towards the bottom plate and contiguous with the wedge portion. The top plate has an outer face 56a and an inner face 56b while the lower plate has an outer face 57a and an inner face 57b opposite the inner face of the top plate taken from the 5 perspective of the bucket floor. Suitably, the upper and lower plates are spaced apart sufficiently to receive therebetween in a tight sliding fit the lip portion of the bucket floor 11 so that the inner face of the upper plate engages the upper face of the bucket floor and the inner face of the lower plate engages the underface of the bucket floor. It will also be seen in Figs. 7 and 8 that the front part of the mounting portion of the lip shroud is shaped to engage ) with the shape of the bucket lip 12 in a tight fit. Both the upper and lower plates have a passage 61 therein, the passages being mirror images of each other. The passage through the upper plate opens at its outer end (or upper end)to the outer face 56a and at its lower end to the inner face 56b while the passage through the lower plate opens at its upper end to the inner face 57b and at its lower end to the outer 5 face 57a. The passage in the outer plate is centred on its vertical axis 64 and defined in part by a portion of the upper jaw member which protrudes inwards towards the vertical axis thereby providing an upwardly facing shoulder 67 which is orthogonal to the axis. The passage is further defined by longitudinally and laterally spaced vertical faces 68 and 69 which are ) separated by the shoulder 67. The passage 62 in the lower plate is a mirror image of the passage 61 and is centred on vertical axis 71, the shoulder being referenced as Item 71 and the two vertical longitudinally and laterally spaced faces being referenced as Items 78 and 79. As can be seen in Figs. 11 and 12, the retainer 42 is an obround ring defined by an 5 annular wall 81 which defines a passage 82 therethrough centred on longitudinal axis 83 and opening at one end to outer face 84 and at the other end to inner face 85. The outer face of the annular wall is "stepped" to match the shape of the inner face of the passages 61 and 62 through the upper and lower plates of the lip shroud. In that regard, the outer face of the annular wall includes annular face 87 which is orthogonal to the axis 83 and the inner face 86 0 and forms a shoulder between laterally and longitudinally spaced vertical faces 88 and 89, those two faces together with the shoulder giving a stepped outer shape to the outer wall. In use, a lip shroud 41 is fitted to the bucket floor by driving it on with a hammer so that the upper and lower plates of the lip shroud are tightly engaged with the upper and lower faces of the floor respectively. Once in the desired position, one retainer 42 is pushed into 6 passage 61 in the upper plate and another retainer is pushed into passage 62 in the lower plate. Once in the desired position, fillet welds are formed at the corner between the inner face of each retainer and the upper or lower face of the bucket floor as the case may be as can be seen in Fig. 10. Notably, the welds pull the retainers tightly into engagement with the lip 5 shroud thereby securing it tightly to the floor. Advantageously, when the lip shroud wears out, it can be replaced by grinding or cutting out the welds 44 and driving the lip shroud off the bucket floor with a hammer. It will be appreciated that the present invention allows for the use of portable milling or grinding wheels to be accommodated to remove the fillet welds 44 if desired. ) While the foregoing description has been given by way of illustrative example of the invention, it will be understood that the invention may be embodied in many other forms and all such forms are deemed to fall within the broad scope and ambit of the invention as described herein.