152 R. OWEN ON THE PURBECK 
In Theriosuchus the breadth and shortness of the antorbital part 
of the skull, in proportion to the part behind, exceeds that in any 
modern broad-snouted Crocodile. Even in the young ‘ Crocodile a 
deux arrétes,’ figured in plate i. of Cuvier’s ‘ Ossemens Fossiles™*, a 
transverse line across the fore part of the orbits equally bisects the 
skull, omitting the mandible. In Z'heriosuchus the same line leaves 
in advance six thirteenth parts of the length of the skull. 
This proportion suggested at first view the immature state of the 
individual. Butof the numerous evidences of Theriosuchus pusillus, 
none were larger than those figured in Plate IX., and several other 
fragmentary evidences of the species had come from still smaller 
individuals. 
I conclude, therefore, that, as in the case of most species notable 
for their diminutive size, immature characters of the larger species 
of the genus are associated with such dwarfishness of the adults. 
I estimate the average length of a mature Vhertosuchus at 
18 inches. The length of the skull, taken as that of the mandible, 
is 3 inches 6 lines. In the articulated skeleton of a modern Croco- 
dile the angle of the lower jaw extends to the third cervical vertebra. 
In Alligator lucius the trunk, from the third cervical to the last 
sacral vertebra inclusive, is nearly equal to two lengths of the skull; 
the length of the tail is 21 lengths of the skull. The trunk of 
T heriosuchus, so defined, includes two lengths of the skull; the tail, 
as indicated by a portion of skeleton preserved, equalled 24 lengths 
of the skull. In the long-jawed Gavials and Teleosaurs the trunk 
includes about 14 length of the skull; but the tail is proportionally 
longer than in the short- and thick-jawed Crocodiles. 
The actions and consequences of a Theriosuchus submerged with 
“a warm-blooded animal” of the size of a shrew or rat in its mouth 
might not excite the physiologist to analyze results and relations to 
palato-narial arrangements. The case is otherwise with a “large 
and powerful mammalian quadruped” in that predicament; its 
amphibicus captor would not escape choking by the mere “ closure 
of the external nostrils.” 
Let any F.G.S., with his head under water, hold his nose and 
open his mouth, and he will experience some trouble at the 
glottis. 
The exclusion of water from the lungs is truly the important 
matter; and I fear my allusion to the mechanism for that purpose, 
which is peculiar to the Neozoic Crocodiles, was too brief to dispel 
a possible haziness of conception of such mechanism. 
A Crocodile, haying seized and submerged a tiger or a buffalo, 
admits the water into its wide unlabiate mouth by the spaces to 
which the thickness of the part gripped keeps asunder the upper and 
the lower jaws. ‘Thus the part of the mouth not occupied by the 
prey is filled with the fluid in which the mammal is being dragged 
and drowned. 
* Quarto, tome v. 2° partie. 
t Quart. Journ. Geol. Soe. vol. xxxiv. p. 423. 
