or EECENT CEOCODILIANS. 135 



The head of the Crocodile first increases in length compared with its width, and then, 

 having arrived at a certain form, increases in width, thickness, and solidity. 



The same change takes place in the head and skull of the Bornean Garial, Tomi- 

 stoma schlegelii, as is found in Miiller and Schlegel's figures of the half-grown and 

 adult skulls in their work. 



It is to be observed that each of the Crocodiles of India and Africa (and it may also 

 be the case with those of America) seems to present two varieties — one with a broad and 

 the other with a narrower face ; this variation occurring in each species appears to me 

 to show that it is more probably a local, or perhaps even sexual variation than a specific 

 distinction. 



If it were a sexual distinction, it might be soon settled by observers in the country 

 where they abound ; but the sex of the skin and the skull sent to Europe is rarely, if 

 ever, marked on the specimens. 



The broad-nosed variety is much more abundant in the Museum than the narrow-nosed 

 one ; and this is against the form of the face being a sexual distinction, as one would 

 suppose that they would be nearly equal in number, unless the narrow-nosed specimens 

 are the males and they are more wary and not so frequently caught. 



Some naturalists might be inclined to regard them as distinct species ; but in the 

 Museum series, large as it is, we have not sufficient materials to decide the question 

 with any confidence. Perhaps, if the skulls of specimens from each locality could be 

 compared, other characters might be found ; but this must be left for my successors in 

 tliis field of research. 



In the short-nosed species the upperside of the intermaxillary bones is short, and the 

 nasal bones are produced between their edges to the edge of the nostril ; and in the genus 

 Halcrosia they are produced beyond it, and form a bony septum between the nostrils. 

 In the long arid slender-nosed species the intermaxillary bones are rather produced 

 behind and the nasal bone does not reach the edge as does the long nostril in the genus 

 Mecistops ; they are considerably short of them ; but still the nasal bones come between 

 the hinder ends of the intermaxillaries, and this character at once separates the skull of 

 that genus from the two genera of Garials which have short nasal bones. 



The skulls of Crocodiles may be separated thus : — 



1. Nasal bone produced, and separating the nostril into two parts. Halcrosia. 



2. Nasal bone produced, and dividing the edges of the nostril. Oopholis, Crocodilus, 

 Molinia {americana), Bomhifrons, Palinia. 



3. Nasal bone not reaching the nostril. Molinia {intermedia), Mecistops. 



The intermaxillary bone in Bomhifrons and Palinia is short and truncated behind. 

 In Halcrosia it is rather produced behind, the straight sides converging to a point. In 

 all the other genera it is produced behind, with the hinder edges converging on the sides 

 and truncated at the end. 



u2 



