112 BRITISH FOSSIL REPTILES. 



fig. 1) are divided from the orbits by a bar of bone developed from the postfrontal (12) 

 and malar (26), and against the inner side of the base of whicli the ectopteiygoid 

 abuts ; the posterior boundary of the fossa is made by the tympanic (28) and squamosal 

 (27). The orbits, having the postfronto-malar bar (12, 26) behind, are surrounded in 

 the rest of their circumference by the frontal (11), the prefrontal (14), the lachrymal (73), 

 and the malar (26). The supraorbital or palpebral ossicle is rarely preserved in fossil 

 specimens. 



The facial or rostral part of the skull anterior to the orbit, is of great extent, broad 

 and flat in the AUigators and some Crocodiles, narrower, rounder, and longer in other 

 Crocodiles, always most narrow, cylindrical, and elongated in the Gavials. The 

 anterior or external nostril is single, and is perforated in the middle of the anterior 

 terminal expansion of the upper jaw. This expansion is least marked in the broad- 

 headed species (compare PL 1 A, fig. 1, with PI. 1 A, fig. 1); in existing Crocodiles 

 and Alligators the points of the nasal bones penetrate its hind border, as at 15, fig. 1, 

 PI. A 2. In the Gavials (PI. 1, fig. 1 a) the nasals («) terminate a long way from the 

 nostril. The Crocodilia resemble the Chelonia in the single median nostril.* In the 

 Lacertilia there is a pair of nostrils, one on each side the median plane, which is 

 occupied by a bridge of bone extending from the usually single premaxillary to the 

 nasals. The plane of the single nostril is almost horizontal in all existing and tertiary 

 Crocodilia. 



On the inferior or palatal surface of the skull (PL 1 B, fig. 2), the most anterior 

 aperture is the circular prepalatal foramen surrounded by the premaxillaries 22 ; then 

 follows an extensive smooth, horizontal, bony plate, formed by the premaxillaries (22), 

 the maxillaries (21), and the palatines (20). The postpalatal apertures are always large 

 in the Crocodilia, and are bounded by the palatines (20), maxillaries (21), pterygoids (24), 

 and ectopterygoids (25). The posterior aperture of the nostril is formed wholly by the 

 pterygoids ; it is shown in PL 1 a, fig. 3, between the bones marked 24. Behind it is 

 the median and lateral eustachian foramen already described, as belonging rather to 

 the posterior region of the head. 



Crocodilus TOLiAPicus, Owe7i. PL 2, 2, B, fig. 1. 



Syn. Crocodile de Sheppy (?), Cuvier. Ossemens Fossiles, 4to, torn, v, pt. ii, p. 165. 



Crocodilus Spenceui, i?i<c/(;/a«(/. Bridgewater Treatise, vol. i, p. 251. "Crocodile 

 with a short and broad snout." Vol.ii, p. 36, pi. 25', fig. 1. 

 — — Owen. Reports of the British Association, 1841, p. 65. 



In proceeding to the comparison, and preparing for the description of the British 

 fossil Crocodilia, I endeavoured, in the first place, to obtain the bones of the species 



* In a skeleton of the Alligator lucius in the Museum of the Royal College of Surgeons, a slender bar 

 of bone is continued from the nasals to the premaxillary, across the median nasal aperture, as it is in the 

 skull of the same species figured in the ' Ossemens Fossiles,' torn, v, pt. ii, pi. i, fig. 8. 



