REVISION ()K JfALACLEMMYS, A GENUS OF TURTLES. 



11 



The food of the diamond-back terrapin consists largely of such crustaceans and 



mollusks us it is able to catch and crush, hut as its jaws arc rather weak it is com- 

 pelled to feed upon the smaller and softer animals of these groups. During excep- 

 tionally high tides it sometimes follows the water into the grassy lowlands, and may 

 be seen to catch and eat insects. The tender shoots and rootlets of sonic of the marsh 

 plants are also eaten, and undoubtedly at times form a very considerable portion of 

 the food. Fresh water seems to he a necessity to the well-being of the diamond-back 

 terrapin, though it can live for a lone- time without it. 



Although it is a common belief in many places where this turtle is found that 

 it is nomadic, moving restlessly from place to place, and that it is aide to make con- 

 siderable journeys in a very short space of time, there is no evidence to support these 

 notions. On the contrary, the individual born in or accidentally transported to a 

 favorable locality probably stays there indefinitely; no other theory will explain the 

 numerous local races and the stories of the reappearance of certain marked terrapins 

 season after season. The former abundance of the diamond-back is a matter of 

 record. At one time hundreds could be seen in a single day where now perhaps only 

 one or two can be found in a season. Thanks to lax laws and ruthless hunters, the 

 species is on the verge of extinction, and before long, unless proper measures are 

 taken, must be numbered among the great host of animals that man has exterminated. 



SEXUAL DIFFERENCES. 



The sexual differences in the genus Malaclemmys, aside from the genital parts, 

 are greater than in any other group of turtles known to me. The females are much 

 larger than the males, they alone attaining the sizes usually cited in descriptions. 

 Their heads are heavier and less pointed, their bodies deeper, and their tails shorter. 

 The males seldom, if ever, reach a greater length than 5 inches"; the shell is flatter 



a Terrapins are usually sold in market by length instead of weight, the measurement being made along the middle 

 line of the lower shell, or plastron, from the lowest point in front to the bottom of the posterior notch. Throughout this 

 paper I follow the popular method of measurement, and such citations of length as are made must lie so understood. The 

 length of the carapace exceeds that of the plastron, sometimes slightly, sometimes considerably, varying with the age and 

 the species of the individual; but so far as I have been able to determine the proportion does not possess sufficient constancy 

 to be of value as a character. The following table shows the variations for a number of specimens in this and certain 

 other respects: 



Locality. 



Chesapeake Hay. 



North Carolina . 



Florida . 

 Texas . . 



Sex. 







Bottom 



shell. 



Topshell. Weight 



TnrfU 8. 



I 

 1 



■', 



6j 



7,:. 

 if 



3H 



! 



I 

 I/, 



I!,; 



41 



t; 



7 



'■;:. 

 IH 



1 1 



a 



■ 



7; 



i,; 



■V.. 

 41 

 4) 



i,':. 

 i;,: 



■"'.'.. 



5J 



V.. 

 7} 



•">■;> 



Ounces. 



If. 

 10 

 16 



it; 

 ■n 

 48 

 is 

 17 

 11 

 15 

 12 

 14 

 11 



it; 



13 



16 



12 



...„„. 



Supposed 



age. 



Ill 

 li 

 5 



5 

 6 



(?) 



