CROCODILES, ALLIGATORS, ETC. 47 



equalling its length. The upper eyelid is very rugose 

 and is frequently produced into a small horn. 



The Caymans are all uniform dark brown or blackish. 



Although reputed to be more vicious and sometimes 

 ready to attack, their habits are otherwise similar to those 

 of Alligators. 



OsteolcemuSy represented by a single species, 0. tetraspis, 

 which reaches a maximum length of only six feet, is 

 restricted to West Africa. Superficially it resembles a 

 Cayman, the snout being short and blunt, while the head 

 is rugose and the space between the eyes raised ; the fourth 

 tooth of the lower jaw fits, however, into a notch in the 

 upper jaw, as in Crocodiles proper, from which it differs 

 only in certain cranial characters. 



In the true Crocodiles, genus Crocodilus, the fourth 

 tooth of the lower jaw fits into a notch in the upper, as 

 in Osteolcemus, not in a pit, as in the Alligators and Cay- 

 mans. Their distribution embraces Africa, Asia, North 

 Australia, and Tropical America. 



The Nile Crocodile, C. 7iiloticus, attaining a length of 

 eighteen feet, was formerly very common in Lower as well 

 as Upper Egypt, and was worshipped by the ancient 

 Egyptians and fed by the priests. Towards the end of 

 the seventeenth century it was still to be met with above 

 Cairo. It occurs at the present day in the rivers and 

 lakes from Wadi Haifa and the Senegal southwards to 

 South Africa ; it is also found in the waters of Madagascar. 



The snout is rather pointed, being once and two-thirds 

 to twice as long as broad at the base. The fingers are 

 slightly webbed, the toes extensively so. The dorsal scutes 

 are arranged in sixteen or seventeen transverse, and six 



