ALLIGATOR MISSISSIPPIENSIS. 55 



four of which are remarkable, each with a strong carina or tubercle, oval at the 

 base and compressed laterally above. These four tubercles are so placed on 

 each side the mesial line, as to make two crests or ridges, with a broad gutter 

 between them. Behind these plates are two others of similar form, but slightly 

 elevated; and on the outer side of these latter again, is a small carinated tubercle 

 over each shoulder. The throat is covered with small and smooth plates. 



The body is elongated, rounded above, full at the flanks and flat below. 

 Superiorly^ it is protected by quadrilateral, strongly tuberculo-carinated plates, 

 disposed in longitudinal and transverse series, forming ridges along the back. Of 

 ' these longitudinal ridges there are eight, the four internal extending the whole 

 length of the body; the two external on each side are shorter, and the outer is 

 shortest of all. Below these tubercles the flanks are covered with smaller 

 plates, smooth, rhomboidal or oval, and arranged in nine or ten longitudinal 

 rows. 



The'' thorax and abdomen are protected by broad, smooth, quadrilateral plates, 

 large on the belly, less extensive between the anterior extremities, and very small 

 between the posterior. These plates are arranged in longitudinal and transverse 

 series; ten of the former and about thirty of the latter. 



The tail is large, long, compressed and thick below, and surmounted above 

 with a double, strongly serrated crest on its anterior, and by a single crest on its 

 posterior half. The vent is a longitudinal fissure, surrounded by many small, 

 smooth plates. 



The anterior extremities are large, strong, and covered above by broad, 

 smooth, rhomboidal or quadrilateral plates; and below by plates still smaller, 

 though of similar form. 



There are five fingers, the second and third, and the third and fourth, slightly 

 palmate; the three internal only are furnished with nails. The posterior extre- 



