466 



CROCODILIA 



CHAP. 



attached to the cross-sticks, indicates the whereabouts of the 

 crocodile when it has taken the bait and has sunk to the bottom. 

 C. johnstoni, of Northern Australia and Northern Queensland, 

 and C. interTnedms, of the Orinoko, are allied to C. cataphr actus,, 

 at least so far as the configuration of the bones of the slender 

 and long snout is concerned. The former is small, scarcely 



reaching the length of 7 feet, while 

 the South American species grows to 

 13 feet. 



C. americanus s. acv.tus. — This 

 species, . which inhabits the West 

 Indian Islands, being there the only 

 representative of the order, occurs 

 also in Florida, and extends through 

 the warmer parts of Central America 

 into Venezuela, Colombia, and Ecuador. 

 Its characteristic feature is a median 

 ridge or swelling on the snout. The 

 length and relative width of the 

 latter varies considerably. The 

 maxillaries sometimes meet dorsally, 

 or they remain separated by the 

 narrow nasals, which in this case 

 reach the posterior corner of the 

 nasal groove. The nuchal scutes 

 vary likewise ; there being often a 

 pair on the side of and 

 another behind the four principal 

 T, tooth -perfora- gcutcs, wliich, as usual, fomi a square. 

 A transverse row of little suboccipital 

 scutes is also common. Largest size about 12 feet long. 



Osteolacm.'us ietmspis s. frontatus. — The only species of this 

 genus inhabits the rivers of the west coast of Africa, from Sierra 

 Leone to the Ogowai. It differs from Crocodilus chiefly by the 

 l)ony septum of the nasal groove, produced by forward extension 

 of the nasal bones. The snout is rather short and stout ; the 

 iipper surface very rugose and deeply pitted, but without ridges. 

 The gular and ventral scutes are ossified, hence the generic name. 

 Total length about 5 feet. 



Alligator. — The fourth mandibular tooth fits into a pit in 



Fig. 111. — Dorsal view of the skull 

 of Crocodilus nmericanus. x |. 

 /', Frontal ; Jg, ju^al ; L, lacry- 

 nial ; M.c, maxillary ; Na, nasal ; 

 P, parietal ; I'mx, premaxillary ; smaller 

 Prf, prefrontal ; Ptf, post- 

 frontal ; Qj, quadrato-jugal ; Sq, 

 squamosal 

 tion. 



