218 REPTILES OF MASSACHUSETTS. 



the shell curve upwards towards the dorsal ridge, but are not 

 as perceptible after curving, and reach the upper ridge, six in- 

 ches anterior to the extremity of the shell. The second lateral 

 ridge commences about seven inches back of the preceding, and, 

 at the posterior extremity, curves up like that ; the abdominal 

 margin makes the third lateral ridge. The posterior extremity 

 of the shell is truncated, and is two and a half inches wide. 



Length of the head and neck, sixteen inches : of the head, 

 nine and a half inches ; width of the head nine inches ; width 

 of the neck, thirteen inches. Diameter of the eye, large. 

 Nostrils just back of the tip of the snout. A large notch in 

 the middle of the upper jaw, which receives the projections of 

 the lower jaw, when the mouth is closed ; on each side of this 

 median emargination of the upper jaw are two others, one on 

 each side of it. Upon the middle and posterior portion of the 

 roof of the mouth, strong spinous processes. 



A portion of the oesophagus of this specimen belongs to the 

 cabinet of the Boston Society of Natural History ; it is com- 

 pactly armed with long firm very sharp spines. 



Anterior extremities, thirty-five inches long, rounded at the 

 origin, compressed in the middle, tapering to a rounded ex- 

 tremity ; in their widest portion, ten inches across. 



Posterior extremities, sixteen inches in length ; for about 

 half their length, nine inches wide, truncated posteriorly, and, 

 as well as the anterior extremities, bordered upon their posterior 

 margin by a deep fleshy fringe or border. 



Length of the tail, thirteen inches ; eight inches wide at the 

 base, tapering to a point. 



Body beneath, covered by a less firm envelope, of a lighter 

 color. 



I am indebted to my friend Dr. Wyman for the accompany- 

 ing plate of this species. 



