1886.] MR. R. LYDEKKER ON SCELIDOTHERIUM. 493 



of the so-called genus Platyonyx, which is either founded on a 

 misidentification, or on characters which cannot be regarded as of 

 more than specific value. 



With these few words of introduction, the descriptive portion of 

 the memoir may be commenced. 



SCELIDOTHERIUM LEPTOCEPHALUM, OwCn. 



The type species is represented in English collections by the 

 imperfect type skeleton from Patagonia preserved in the Museum of 

 the Royal College of Surgeons, and by two imperfect skeletons 

 collected by Bravard in the Argentine Republic and preserved in 

 the British Museum. The skull from the latter country, figured by 

 P. Gervais in the ' Mammiferes fossiles de I'Amerique meridionale ' 

 (Castelnau's Voyage), pi. xi. fig. 1, apparently also belongs to this 

 species. 



The type cranium is considerably damaged, but the two British- 

 Museum crania (Nos. 3/308 and 32995), taken together, exhibit 

 nearly all the important features ; the second of these specimens is 

 figured from the lateral aspect by Sir R. Owen in the 'Philosophical 

 Transactions' for 1857, pi. viii. fig, 1. In Plate XliVI. of the 

 present memoir I have figured the former specimen, the occiput being 

 restored from No. 32995. In the figured specimen the greater 

 portion of the nasals is preserved, and its more important characters 

 are as follows : — 



The facial profile is strongly curved, and presents a well-marked 

 frontal protuberance behind the orbit ; the cranium is of moderate 

 width, and the nasals of great relative length, being when complete 

 at least equal to one half the total length of the frontal aspect of the 

 cranium. In correlation with the elongated nasals the facial portion 

 of the maxilla is lengthened, and a large portion of it appears on the 

 frontal aspect. The lachrymal is not very prominent, and the 

 aperture of its canal looks directly outwards. The anterior border 

 of the zygomatic process of the maxilla is inclined backwards ; the 

 fronto-parietal ridges are widely separated, and the interdental portion 

 of the palate is not excessively narrow. 



The mandible associated with the figured cranium has an elongated 

 symphysis, the portion in advance of the teeth being nearly twice 

 the length of the whole dental series, and the superior border of the 

 anterior portion of the ramus nearly straight. 



The more important measurements of the figured skull are as 

 follows : — 



Length of broken nasals 0'270 



Length of facial part of maxilla 0-1 70 



Width of the two occipital condyles. ... 0'108 

 Length from condyle to last tooth .... 0*242 



Length of dental series 0'113 



Length of mandibular symphysis .... 0*156 

 Interval between hinder border of sym- 

 physis and last tooth 0*350 



Interval between do. and first tooth. . . . 0*050 



