Chap. II. 



THE CIIELYUID.E. 



335 



SECTION V , 



FAMILY OF CHELYOIDiE. 



Tile fiiniily of ChelyoidiK, as characterized below, embraces only one genus, the 

 Clielys of South America. As limited by former observers, the type of Pleuro- 

 deres, to which Chelys l)elongs, combines features which iire parallel to those that 

 characterize the families of Trionychidoe, Chelydroida?, Cinosternoidae, and Emydoidas. 

 These ])ecuharities would seem to be remarkably blended here, if this type were 

 to constitute a single family. I believe, however, that tliis is not the case.^ I 

 have, at least, satisfied myself already, that the Chelyoidae are very different from 

 the other Pleuroderes, as the following description may show. 



The dorsal part of the vertebral column, from the first dorsal vertebra baek- 



' Of all tlif types of Testudinata, that of Clicly- 

 (liiia is tlic only one, for the examination of wliicli I 

 have not been able to secure ample materials. Hav- 

 ing however myself, when student in the Univer- 

 sity of IMiinich, made most of the skeletons which 

 arc fijjiinil in the Atlas to AVagler's Natiir. System 

 Amphibien, 1830, I have derived sufficient informa- 

 tion from his illustrations of this subject to satisfy 

 myself that several families are still included under 

 the LToiip called Eloditcs Pleuroderes, by DunuM-il 

 and IJibron, (Erpet. gener., 1835.) The first allusion 

 to the projiriety of considering them as a distinct 

 group may be found in .T. E. Gray's Synopsis of the 

 Genera of Reptiles, (Ann. of I'hilos., 1S2.'),) where 

 they are enumerated as a sub-family of tlic Etny- 

 dt)ida', under the name of Chelidina. Soon after- 

 wards Fitzinger considered them as a distinct family, 

 under till- name nf t'lulydoidea, (Neue Classif., 1820.) 

 This family was afterwards adopted bj- Wiegmann, 

 under the name Chelyda>, (Ilandb. d. Zool., 1832.) 

 then std)dividcd into two sub-families bj- Canino, 

 niiih'r (he names of Ilj'draspidina and Chelina, (Clie- 

 limioruin. Tab. Anal., 183G.) These two divisions 

 are c(in>idcred as families by Kit/.inger, in his latest 

 work, (Syst. Amph., 1843.) under the names of Ily- 

 driuspides and Chel}'da\ Gray, however, considers 

 th« in still as one family, under the luime of Chelididie, 



(Cat. Brit. Mas., 1844.) I hold that the separation 

 of the Chelyoidae from the llydraspides, as a distinct 

 family, is founded in nature. From the examination 

 of several specimens in the Museum of the Essex 

 Institute in Salem, I have satisfied myself that the 

 genus Chelys of Dumeril truly constitutes of itself a 

 natural family. But I am by no mean$ convinced 

 that the genera referred to the family of llydraspides 

 arc so closely allied to one another as to form one nat- 

 ural family. There are those among them which re- 

 call the Cinosternoids, while others resemble more the 

 Einydoids. I am, therefore, inclined to believe, though 

 I have not the means to show, that as Chelys consti- 

 tutes a natural family among the Pleuroderes, analo- 

 gous to the Chelydroidai among the Cryptoderes, so 

 does Sternotha-rus correspond to the Cinosternoids, 

 while the other genera Cflrres[K)nd to the bulk of the 

 Emydiiids. thus forming two natural families, which 

 may be called Sternothwroida; and llydraspides. It 

 may be, however, tliat several of the genera of the 

 llydraspides ditt'er still more from the others than Uie 

 sub-families of Emydoid;e among themselves, as, for 

 iii>lani'e, Podociuinis and Chelodina. This tvpe of 

 Pleuroderes re([uircs yet to be thoroughly studied, in 

 all its ramitications, and minutely compared with the 

 corresponding types of Cryptoderes, characlerized in 

 the following pages as distinct families. 



