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Show 1886.] MR. R. LYDEKKER ON SCELIDOTHERIUM. 495 the symphysis is greater than in 8. leptocephalum, the interval between the hinder border of the symphysis and the first tooth is very considerably less. The superior border of that portion of the mandible in advance of the teeth is moreover inclined strongly upwards. The following dimensions may be compared with those of S. leptocephalum :- Length of facial part of maxilla (about) 0*135 Width of the two occipital condyles 0*095 Length from condyle to last tooth 0*258 Length of upper dental series 0*105 Length of mandibular symphysis 0*175 Interval between hinder border of symphysis and last tooth 0350 Interval between do. and first tooth 0*032 I will now direct attention to the astragalus. Unfortunately the one specimen of this bone, associated with the cranium, is imperfect, although sufficient remains to show that it differs from the corresponding bone of the type species by the great prominence of the external trochlear ridge, which projects far above the level of the internal tuberosity. In Plate XLIX. fig. 4, there is represented an astragalus from a cavern in Brazil, which, although of larger size than Bravard's specimen, agrees precisely in structure, and either belongs to a male of the present form or to an allied species; and I think a comparison of this figure with that of the astragalus of S. leptocephalum will leave no doubt as to the specific distinctness of tbe two forms. This astragalus agrees precisely with the corresponding bone of a hind foot belonging to a perfect skeleton figured by Dr. Burmeister in the Monatsb. k. preuss. Ak. Wiss. for 1881, plate facing p. 380, fig. 2, and referred (on the authority of Sir R. Owen's figure of the cranium of the present form) to a large male of S. leptocephalum. A tibia from Brazil, associated with the figured astragalus, presents a structure of its distal surface modified to accord with this peculiar articulation, which is different from that of the tibia of S. leptocephalum; and there are equally well-marked differences in some of the other bones of the present form to which I shall allude on another occasion. Whether or no the larger bones mentioned above belong to male individuals of the same species as the cranium, I think sufficient evidence has been adduced to show that both the form to which the latter and that to which the former belonged are specifically distinct from S. leptocephalum. Confining, however, attention to Bravard's specimen, it is quite evident that this form is distinct both from S. tarijense (in which the mandible is of quite a different type) and S. (Platyonyx) brong-niarti (in which the nasals are very short and the premaxillas aborted) ; and since it appears impossible to identify it with either of the ill-defined Brazilian forms mentioned above to which specific names have been assigned, I propose that it should be known as |
