DWARF CROCODILES AND DIMINUTIVE MAMMALS. 151 
of the upper canines. The twelfth tooth, counting backwards, 
assumes the lamellate triangular shape of striate crown charac- 
teristic of the superior sectorials ; and the inferior ones were lodged, 
like those above, in a common depression of an outer alveolar wall, 
developing the ridges dividing such depression into the dental re- 
cesses, as shown in fig. 7. 
This approximation to a lacertian dental character might seem 
ground for something more than a family section of the Order Cro- 
codilia. But the quasi-pleurodont attachment of the hinder teeth 
in Theriosuchus is only an extension of the character affecting some 
of those teeth in existing species of Crocodile*, and successional 
teeth, or their indications, are in crocodilian relation with the roots 
of the teeth to be displaced. 
In the cranial platform of Theriosuchus, fig. 1, the median parictal 
part of the hind border is less convex, and the two outer parts are 
more concave, by reason of the further backward production of the 
mastoids (12), than in the contemporary dwarf Crocodile which I 
have called Nannosuchus. The lateral borders of the sculptured 
part of the platform are more convex than in Gontopholis or Petro- 
suchus. This is owing to the greater proportion of the outer and 
posterior angles of the platform, which is abruptly depressed below 
the level of the sculptured surface of the mastoid, and which be- 
comes smooth like the contiguous and lower-placed tympanic. This 
character, shown in the subject of fig. 1, Plate 1X., usefully indicated 
fragmentary parts of the skull of other individuals of the species. 
The supratemporal vacuities (T) are relatively larger than in Gonio- 
pholis. The intervening tract of the parietal (7), more canaliculate 
than in the larger species, is divided by a mid ridge in two of the 
cranial specimens, and partially so in the more complete skull, 
fig. 1. No palpebral ossicle is preserved in the orbit, 0; the poimted 
ends of the nasals are produced so as to divide the outer nostril 
into two (fig. 1,, 7), as In some specimens of Crocodilus wiger ; 
were this a character of generic value it might unite Z’heriosuchus 
with Halcrosia, Gray t. 
The alveolar part of the maxillary in which the canines are de- 
veloped makes a corresponding convex extension of its outer border, 
as in Goniopholis. The extent of the ‘symphysis mandibule’ and 
the angle of divarication of the same are shown in fig. 2. 
The matrix being removed from the palatal surface of the skull, 
fig. 2, exposed the orifice of the Eustachian canal, ¢, the palato-naris, 
pn, the pterygoids, 24, the palatines, 20, portions of the palatal plates 
of the maxillary, 21, and the pterygo-maxillary vacuities, y. The 
vertebrae, fig. 12, of Theriosuchus are amphiplatyan. The humerus, 
fig. 8, and the femur, fig. 9, have the Crocodilian structure. 
* Thave noted it in the Alligator niger. ‘“No.'765. The right ramus of 
the lower jaw, from which the posterior part of the inner alyeolar wall has 
been removed, showing the five posterior teeth lodged in a common alveolar 
groove.” Osteological Catalogue, Museum of the Royal-College of Surgeons, 
Ato, vol. i. p. 167 (1853). 
t Trans, Zool, Soc, yol. vi, p. 135, 
