. Bulletin of the British Museum (Natural History). 298 D. S. BROWN. 1cm Fig. 24 Tncleidus seeteyi Andrews, tooth of holotype showing ornamental ridges: a and c, axial; b, lingual; d, buccal aspect. special process for ailiculation with the basisphenoid (labelled '. by Andrews). They also differ from the pterygoids of Muraenosaurus in that there is no prolonged process for contact with the ectopterygoid. and it must be assumed that the missing ectopterygoid in the present species was proportionally larger than in that genus. The vomers are fused to form a single median element which
. Bulletin of the British Museum (Natural History). 298 D. S. BROWN. 1cm Fig. 24 Tncleidus seeteyi Andrews, tooth of holotype showing ornamental ridges: a and c, axial; b, lingual; d, buccal aspect. special process for ailiculation with the basisphenoid (labelled '. by Andrews). They also differ from the pterygoids of Muraenosaurus in that there is no prolonged process for contact with the ectopterygoid. and it must be assumed that the missing ectopterygoid in the present species was proportionally larger than in that genus. The vomers are fused to form a single median element which has the shape of an arrow- head and resembles closely that of Muraenosaurus. Welles (1952 : 98) misidentified this bone as the nasals, which are not known as separate elements in Jurassic plesiosaurs. The preserved elements of the braincase were described and figured fully by Andrews (1910). The form of the occipital condyle and the paroccipital processes are as in Muraenosaurus, and thereby differ from those of Crypioclidus (cf Figs 23 and 2). The lower jaw (Andrews 1910: pi. 8) differs from that of Muraenosaurus (which it otherwise resembles closely) by having only 17 tooth sockets on each ramus. Of these the 2nd to 8th are the largest, but the size does not greatly diminish posteriorly, and the most posterior may be described as of medium size. The fme state of preservation permits the orientation of the teeth to be assessed; this was just as in C. eurymerus, specimen (pp. 262-3). The right ramus of the lower jaw contains in silu eight complete teeth, and in addition several isolated teeth are preserved (Fig. 24). These are ornamented with many longitudinal ridges which, as in Muraenosaurus, are found all round the teeth and especially on their lingual sides. By comparison with Crypioclidus (Fig. 1) the skull of Tricleidus (Fig. 22) is relatively short in the snout region, relatively high posteriorly, and has fewer teeth. It therefore resembles more closely reconstru
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