CuAP. III. THE GENUS SPIiARGIS. 371 



lime l)y puljlishing full quotations of all the -works in wliieli notices respecting 

 our Turtles may be found. Every student, who may wish to make himself familiar 

 with this branch of our science, will find ample references to all the works worth 

 consulting in any general treatise on Herpetology. I have only alluded to the 

 subject in detail where I had reasons to dissent from my predecessors. 



SECTION II. 



TUE GENUS SPHARGIS. 



The genus Sphargis was first pointed out by Merrem in 1820, under the name 

 which is now generally adopted for it.^ With the scanty materials I have on 

 hand, I feel it the more difficult to draw up a description of the generic characters, 

 as the habits of these Turtles are little known, and all the specimens I had an 

 opportunity of seeing in America were adults, thus affording no opportunity for 

 an appreciation of the changes they undergo with age. In the study of genera 

 it is very important to compare young and adult specimens, as, from the differ- 

 ences they exhibit, it is generally possible to ascertain what constitutes generic 

 characters, in contradistinction to family and specific characters. As far as I can 

 judge from analogy, and by comparison with the genera of the Chelonioida;, the 

 following may be considered as generic characters. 



The arch of the top of the skull is highest over the hind end of the brain- 

 box, and grows narrower and lower thence forward to the eye orbits. The upper 

 surface falls from over the hind end of the brain-box backward ; it is depressed 

 over the front end of the brain-box. The frontal region falls from the hind end 

 forward. The upper edge of the opening of the nasal cavity is nearly on a level 

 with that of the eye orbit. The intermaxillaries rise considerably above the level 

 of the lower edge of the eye orbit ; they are very thick above, and taper to a 

 sharp edge below. The edges of the notch of the front end of the alveolar wall 

 of the mouth meet the edge of the lateral notch of each side, on the maxilla- 

 ries, near the suture with the intermaxillaries. The three notches occupy the 

 alveolar edge of that part of the mouth which underlies the nasal cavity. The 

 horizontal alveolar surface of this part of the mouth rises steeply forward ; it is 



a 



* In 1828, Fleming called it Coriudo, in imitation Sc_vtini\ in the plates to his Nat. Sysf. der Anipli.. : 



of the name Testiido ; in 1829, LcSueur, in Cuvier's few copies of which bear that lettering; but he finallj- 



Eegn. Aniin., proposed the new name Dermochelys adopted LcSueur's name, changing it however to 



for it; in 1830, Wagler introduced still another name, Dermatoclielys. 



