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 LEPTOCEPHALU M, Owen. 
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 ‘Mammiféres fossiles de Amérique méridionale ’ 
(Castelnau’s Voyage), pl. xi. fig. 1, apparently also belongs to this 
species. 
eThe type cranium is considerably damaged, but the two British- 
Museum erania (Nos. 37308 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, pl. viil. fig. 1. In Plate XLVI. 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 promineut, 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°170 
Width of the two occipital condyles.... 0°108 
Length from condyle to last tooth .... "242 
Length of dental series; . ..06. 000.00 0113 
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 
