G34 BRITISH FOSSIL REPTILES. 



The convenience of these three genera of ProcccHan Crocoflilia, although they agree 

 in palatonarial and vertebral characters, will probably ensure their retention; but 

 Tomistoma, Oopholis, Ilalcrosia, Palceomchus, Rhjnchosuclms, Jiamjjhosfoma, Mecistops. 

 Boiiihifrons, Palinia, Moliuia, Caiman, Jacare, &c., into which they have been subdivided, 

 exemplify the evil of " encumbering the science with a multitude of names " (loc. cit., 

 p. 128), — an evil which, if the " names " do not represent " generic distinctions," cannot 

 be laid to the charge of the " Palaeontologist." 



At least, the "small fragments of the fossil skeleton" (ib., p. 128) on which the 

 genus GomojjhoUs was originally founded have subsequently been proved, by acquisition 

 of other parts, to have indicated accurately that well-marked and interesting addition 

 to the recorded modifications of the Crocodilian type. Those of the vertebral and 

 cranial structures have, indeed, proved to be not only of generic, but of family value. 



Genus — Petrosuchus, Owen} 

 Species — Petrosuchus levidens. Crocodilia, Plate 41. 



This genus and species of Crocodile is founded on the portion of skull and mandible, 

 figured in Plate 41. The skull is imbedded in the same limestone of the Middle 

 Purbecks, now quarried at Swanage. It was discovered in a block with the upper 

 surface (ib., fig. 1) exposed. This surface is partially weathered, but shows here and 

 there a faintly wrinkled natural sculpturing. The upper temporal apertures are larger 

 than the orbits. In front of these the skull contracts more rapidly tliau in GoniojilwUs, 

 and presents, as far as it is preserved, a slender form of face approaching to the propor- 

 tions of that in the modern Crocodilus cataphractus^ and in the Tertiary Crocodilus champ- 

 so'ides (p, 115) ; but the more rapid contraction in front of the orbits is gavial-like, and there 

 are other characters indicative of a nearer affinity than in Goniopholis to the Teleosaurian 

 group. This affinity is decisively marked by the larger relative size and more advanced 

 position of the palatouaris (ib., fig. 2, »), into the formation of which the diverging hind 

 ends of the palatines (ib., fig. 2, 20) enter in a larger proportion than in Goniojj/iolis. 

 The basisphenoid (ib., ib., .5) is more produced, and the pterygoid (ib., ib., 24) contracts 



Saurian (Diplosaurus) with essentially the skull and teeth of a modern Crocodile, and the vertebrae of its 

 predecessor from the Trias." 



When the cranial characters of this Crocodilian are made known it will be of moment to compare the 

 temporal apertures on the upper surface and the palato-narial apertures on the under surface of the skull. 

 When the dental characters of the same fossil are described and figured we may be able to determine 

 whether they are those of the broad-faced procoelian Crocodiles and Alligators or those of Goniopholis. 



1 Gr. ■nerpos, rock, and 1r)v-)(^vi, an Egyptian name of the Crocodile. 



^ Cuvier, 'Ossem. Foss.,' 4to, tom. v, part ii, pi. v, figs. 1 and 2; Gray, 'Trans. Zool. Soc.,' vol. vi, 

 pi. xxxii, fig. 2. 



