10 FOSSIL REPTILIA OF THE 



zygomatic arches, as 8 to 10 in Nannosuchus ; in Croc, niger the platform is little more 

 than half the breadth of the skull taken across the hind part of the parieto-mastoid or 

 upper temporal apertures ; in Croc, pahistris the platform occupies half the breadth 

 of the skull taken at the same part. 



The upper temporal apertures (t) have the same relative size as in Petrosuchus, but 

 they differ in shape, being less circular, the longer diameter being longitudinal, or in 

 the skull's axis. As far as the orbits are preserved these do not exceed in size the 

 upper temporal apertures. This character of the Mesozoic Crocodile is retained in the 

 present dwarf species. A super-orbital bone strengthened the upper eyelid ; it retains 

 its connections vi^ith the frontal (H), post-frontal (12)^ and pre-frontal (I'l) in the left 

 orbit (o) ; but has become slightly detached in the right orbit (o'). The nasal bones 

 (15) terminate in a point distant from the external nostril by rather more than the 

 diameter of that aperture, which accordingly is single and exclusively bounded by the 

 premaxillaries. In this character Crocodilins cataphr actus and Croc, intermedius 

 resemble Nannosuchus ; but the upper jaw is longer and more slender in proportion in 

 both these existing Crocodiles than in the Purbeck species ; in both, also, the upper 

 temporal apertures are relatively smaller than in Nannosuchus. 



In the character of the nasal bones and conformation of the external nostril Nanno- 

 suchus resembles Goniopholis} but the supra-temporal apertures are more oblong and 

 the maxillaries are not so out-swollen as they approach the premaxillaries. The facial 

 part of the skull, from the front border of the orbit forwards, equals the extent of the 

 skull from the same part to the occiput in Nannosuchus ; in Goniopholis the facial part 

 of the skull, so defined, is one third longer than the extent behind. The mutilated state 

 of the unique skull of Petrosuchus ^ prevents a similar comparison being made. 



The sculpturing of the upper surfaces of the exposed parts of the skull in 

 Nannosuchus presents the common Crocodilian character of minute subcircular pits, 

 leaving a reticulate disposition of the intervening bone. 



Genus — Theriosuchus,^ Owen. 

 Species — Theriosuchus pusillus. Plate III, figs. 3- — 16 ; Plate IV. 



This Crocodile, somewhat smaller in size than the preceding species, approaches 

 nearer to the type of the broad-faced Alligators in the proportion of the antorbital part of 

 the skull. 



The dentition is more modified than in any other known Crocodile, recent or extinct, 

 and approaches that which characterises the Theriodont order of Triassic Reptilia. 



1 Supplement, &c., No. viii, Plate V, fig. 1,^. ^ Supplement, &c,. No. viii, Plate VI, fig. I. 



^ Gr. drjfjiov, wild beast ; rrov^vf, crocodile. 



