198 FOSSIL REPTILES. 



stronger scales than in the preceding, each elevated in the 

 centre with a bulky projecting ridge. This gives them the ap- 

 pearance of being more vigorously armed. 



The fourth species is the crocodilus galeatus, Cuv., Siamensis, 

 Schneider. Its distinguishing character consists in two trian- 

 gular osseous crests implanted one behind the other on the 

 central line of the cranium. It resembles almost in everything 

 the common species of the Nile, attains the length of more than 

 ten feet, and inhabits the rivers of Siam. 



It is only known by the description given by the French 

 missionaries at Siam. 



The crocodilus biscutatus of Cuvier, black crocodile of Adan- 

 son, is the fourth species. The muzzle is more elongated than 

 in the preceding species, but less so than in that of St, Do- 

 mingo. The two middle longitudinal lines of the crests are less 

 projecting than the lateral ones, and these last are somewhat 

 irregularly disposed. The nape is armed with only two large 

 pyramidical scales on its centre^ and two small ones in front. 

 The number of transverse scales, as far as behind the thighs, is 

 only fifteen. The scales of the two longitudinal central lines 

 are broader than they are long. 



This species has been found in the river Senegal by Adan- 

 son. This naturalist says that it is blacker and more ferocious 

 than the common species, which is also to be met with in the 

 same river. 



The slender-muzzled crocodile of St. Domingo, crocodilus 

 acutusy Cuv., is the fifth species. The muzzle is more slender 

 than that of all the other crocodiles properly so called. 



The breadth of the head, taken at the articulation of the 

 jaws, is comprised twice and a quarter in the length. The 

 length of the cranium is little more than a fifth of the total 

 length of the head. The males, however, have all these pro- 

 portions a little shorter than the females, approximating in this 

 respect to the females of the common crocodile, especially when 

 young. On the middle of the chaftron, a little in front of the 



