REVISION OF MALACLEMMYS, A GENUS OF TURTLES. 1 .'! 



MALFORMATIONS. 



During my investigations I have met with si very considerable number of 

 specimens of diamond-back terrapin which in one way or another were malformed, 

 either congenitally or as the result of some injury or disease. Malformations of the 

 latter character are of no special interest, except in so far as they show the ability of 

 the animal tu recover from its injuries and the futile effort on the part of nature to 

 regenerate the lost parts. In any large collection of terrapin it is easy to rind 

 individuals that have lost a foot. Occasionally both the feet on one side or both feet 

 of one pair will lie missing and I saw one individual in which all four feet were gone. 

 After such an injury the stump usually heals over smoothly, hut occasionally 

 irregular growths, not at all like the missing member, appear, and the result may he 

 a curiously branched, stumpy termination. 1 have never seen a specimen which 

 showed even an approximately perfect regeneration of any lost part. Injuries to the 

 body, unless too severe, are often survived. One individual I observed in a pound 

 at Cristield, Md., had lost about one-third of the posterior half of its body, including 

 its left hind leg. The wound, which must have exposed the body cavity, had healed. 

 and the animal was apparently none the worse for the injury. 



A disease similar to necrosis of the bone has been observed in a large number 

 of terrapins, especially those confined in pounds. The first appearance of the 

 disease is a small white spot on the plastron. This gradually enlarges, pushing its 

 way through the, scale, and a cheesy nodule from the size of a pin head to that of an 

 almond kernel drops out, leaving a more or less deep cavity in the bone. Usually 

 this cavity speedily becomes covered with sear tissue, but in some instances it grows 

 until eventually a large area of the shell is eaten away. In se\ ere eases death results, 

 but I saw-one individual which had recovered after more than half the plastron had 

 disappeared. In quite a number of terrapin from South Carolina and in a few 

 from Chesapeake Bay 1 have found similar cheesy nodules in the skin of the neck 

 and legs. There was always an aperture in the skin, but no amount of pressure 

 could force out the contents. When the, tumor was opened a nodule dropped out 

 which on examination showed a concentric structure. The skin surrounding it was 

 considerably inflamed, but there was no suppuration and the wound healed quickly. 



The congenital malformations, with one exception, affected the plates of the 

 carapace and were of the most varied character. The most common'was the appear- 

 ance of supernumerary plates, one or more small scales being intercalated among 

 the costal plates. Another, and a very common malformation in one species, was 

 the longitudinal division of the nuchal or the vertebral plates. This seldom led to 

 any rearrangement of the scales, but in one case, on a terrapin from Chesapeake Bay, 

 there was a double series of perfectly formed vertebral plates arranged alternately 

 down the full length of the carapace. The exception mentioned above was a dwarfed 

 animal, which had a very broad and short shell slightly twisted to one side; there 

 was no trace of injury and the terrapin was apparently very old. 



THE AGE THAT TERRAPIN MAY ATTAIN. 



Professor Agassiz was of the opinion that most of our turtles, the present 

 species included, may attain a very great age and continue to grow almost indefi- 



