14 BULLETIN OF THE BUREAU OF FISHERIES. 



nitely. It is true that there is almost indisputable evidence to support this assertion 

 in regard to some species, but for nearly all there is a limit, in size at least. 



For the diamond-back terrapins the maximum size is about 9 inches, very rarely 

 exceeding 8, and is attained probably at the age of 15 or 20 years. It is quite 

 possible, of course, that the turtles live for many years after attaining their growth, 

 but in this event we should expect to find the plates of the shell worn perfectly 

 smooth, a condition I have never observed in any species except the Texas terrapin, 

 which, probably as a result of the warmer and more uniform climate of its habitat, 

 seems to grow more continuously than its relatives. I am therefore led to believe 

 that from 20 to 25 years is the average duration of life for the turtles of this genus. 



DISCUSSION OF SPECIES. 



Key to tin species and subspecies ofttu genus Malaclemmys. 



a. Carinse of vertebral plates never tuberculate. Atlantic coast species. 

 b. Head large to medium size; sides of carapace subpa rail el; southern form ranging 



north about to ('ape Hatteras M. centrata. 



bb. Head medium to small; carapace widest posteriorly; northern form ranging 



from about Cape Hatteras to Buzzards Bay .1/. a ntrata conct ntrica. 



aa. ( 'arinre of vertebral plates more or less tuberculate, at least in the young. Gulf coast species. 



c. Each plate of the carapace with a large central yellow or orange blotch M. macrospilota. 



cc Plates of carapace without yellow blotch. 



d. Carapace uniform black or dark brown, top of head and upper lip dark M. pileata. 



dd. Carapace uniform light brown or with traces of concentric markings; upper 



lip and top of head nearly always white M. I i Horn lis. 



Malaclemmys centrata (Latreille). The Carolina Terrapin. Pis. II, III, X (fig. 1 |, and XII (lig. 1). 



1802. Testudo centrata Latreille, Hist. Nat. (les Rept., I. p. 145. 



1803. Tr studo a ntrata Paudin. Hist. Nat. Gen. et Partic. des Rept., II p., 153. 

 1814. Emys centrata Schweigger, Prodrom. Iconog. Chelon., p. 32. 



1825, Emys a ntrata Say, Jour. Acad. Nat. Sci. Phila., IV, p. 205 I part). 



1830. Terrapene pal-mtris Bonaparte, Test. Gen., p. l.">7. 



1830. Testudo palustrU LeConte, Ann. Lye. N. Y.. Ill, p. 113 (part). 



1831. Ennis centrata Gray, Synopsis Rept., pt. 1, p. 27 i part). 



1834. Emys concentrica Bell. Monog. Test. (part?). (This work not examined). 



1835. Emys concentrica Dumeril &Bibron, Erpetol. Gen., p. 261 (part). 

 ls4J. Emys terrapin Holbrook, North Am. Herp., I. p. 87, PI. xn (part). 

 1842. Emys terrapin DeKay, Fauna N. Y., II (parti. 



1st I. Malaclemmys conct ntrica Gray, Cat. Tort. &c.,Brit. Mus., p. 28 (part). 



1857. Malacoclemmys palustris Agassiz, Contr. Nat. Hist. U. S., I, p. 4H7, pK 1 ami 7a (parti. 



1862. Clemmys i< rrapin Strauch, Chelon. Studien, p. 132 (part?), not examined. 



1865. (Xemmys l< rrapin Strauch, Vertheil. Schildkr., p. 90 (part?), not examined. 



1865. Emys terrapin Maximilian, N. A. Acad. Leop. Carol., XX. Ill, I, p. 16. 



18.S9. Mtilarotit mintizlfrmiii u Unulengcr, Cat. chelon. Brit. Mus., p. 89 I parti. 



1899. Malaclemmys a ntrata Jordan, Man. Vert. 8th ed., p. 209 (parti. 



Typt locality. — Bosc's material, on which Latreille's description was based, probably came from 

 the neighborhood of Charleston, South Carolina. 



Distribution. — Littoral region of the eastern United States from the neighborhood of Cape Hatteras 

 southward to the coast of Florida. 



i naracU rs. — When looked at from above, the shell of this terrapin is ovoid in outline, the greatest 

 width being behind the middle and across the fourth vertebral plate"; the front is nut very deeply, some- 

 times scarcely at all, notched. From the side view the shell is seen to be highest near the middle, the 

 tops of the crests of the second and third vertebral plates usually being the highest [Joints, from which the 

 curve downward is gradual, both backward and forw-ard; the lower margin of the carapace slopes gently 

 downward from the front to a point near the suture between the seventh and eighth marginal plates, 



a In this connection see Bangs (1896), in which article the occurrence of M. centrata [ tl M. terrapin") in Buzzards Bay. 

 Massachusetts, is recorded and remarks are made on the variations observed in a large series of the specie- 



