122 BRITISH FOSSIL REPTILES. 



fig. 2, PI. 1 B, which are not perforated ; so that there are no foramina anterior to the 

 bony nostril, as in PI. A 2, in the bone marked 22. These foramina are not, however, 

 absent in all Alligators ; the skull of the Allic/ator sderops, figured by Cuvier (tom. cit., 

 pi. i, fig. 7), shows them, as do all the species of true Crocodile the skulls of which are 

 figured in the same plate. There is one character by which the Crocodilus Hastingsia 

 differs from all known species of both Crocodile and Alligator : it is that afforded by 

 the broad and short nasal bones (i.'5, fig. I, PI. 1 A), which do not reach the external 

 nostril ; this being formed, as in the Gavials, exclusively by the premaxillaries 22. 



In the general proportions, however, of the skull in question, especially the great 

 breadth, shortness, and flatness of the obtusely-rounded snout, it resembles that of the 

 Alligators more than that of any known species of true Crocodile, the length from the 

 tympanic condyle to the end of the snout being to the breadth taken at the condyles 

 as 16 to 9. 



The following are dimensions of the fossil in question : 



Feet. Inches. Lines. 

 Length of skull from the angle of the lower jaw to the 



end of the snout 



Do. from the tympanic condyle to ditto. 



Do. do. to the orbit 



Do. from the orbit to the external nostril . 



Breadth of the skull across the tympauic condyles 



Do. the orbits 



Do. the external nostril . 



Longest diameter of upper temporal aperture 



Do. the post-palatal vacuities 



Depth of the lower jaw at the posterior vacuity . 



Depth of the occipital region ..... 



The occipital region of the skull (PI. I A, fig. 2), in the proportion of its breadth to 

 the depth of the lateral parts formed by the conjoined paroccipitals (4) and mastoids (s), 

 resembles that of the true Crocodiles rather than that of the Alligators, in which that 

 region is proportionally deeper than in the Crocodiles ; the vertical extent of the 

 supraoccipital is less, and that of the conjoined parts of the exoccipitals above the foramen 

 magnum is greater ; the vertical extent of the descending part of the basioccipital is 

 also greater in proportion to its breadth than in the Alligators. The proportion of the 

 basisphenoid (.5) and of the conjoined parts of the pterygoids (24) which appear in this 

 view (fig. 2), is less than in the Alligators, but is greater than in most Crocodiles, thus 

 presenting an intermediate character ; but the entire exclusion of any part of the 

 posterior nostril from this view is a character of the Alligators, and is due to the 

 horizontal plane of that aperture in them, and to its position in advance of the posterior 

 border of the pterygoids, from which it is partitioned off usually by a bony ridge. 

 The posterior nostril has the same position and aspect in the Crocodilus Hadingsice, 

 and these characters of the posterior nostril are perhaps more distinctive between 



