64 SYSTEMATIC PALEONTOLOGY 



Chelone sp. 

 Plate XXVI, Fig. 5. 



Description. — A fragment of the proximal portion of the scapula of 

 a very large specimen; badly weathered but showing the scapular part 

 of the humeral cotylus and the region of attachment of the coracoid. 



Occurrence. — Calvert Formatiox. Plum Point. 



Collection. — Maryland Geological Survey. 



Order CROCODILIA. 



Suborder EUSUCHIA. 

 Family CROCODILIDAE. 



Genus THECACHAMPSA Cope. 



Thecachampsa Cope, 1867, Proc. Acad. Nat. Sei. Pbila., vol. xis, p. U3. 

 Thecachampsa Cope, 1869, Proc. Acad. Nat. Sci. Phila., vol. xxi, p. 11. 

 ThecacJiampm Cope, 1882, Amer. Nat., vol. xvi, p. 983. 



In the original description the form is separated from Crocodilus by 

 " the entire hollowness of the external stratum of 'the crowns of the 

 teeth, and their composition of closely adherent concentric cones. 

 These internal cones, which number at least three, may be homolo- 

 gous with the included crowns of the successional teeth of other 

 Crocodilia, but they must be regarded as functional in a physiological 

 sense, since they compose the bulk of the crown of the tooth within." 



In 1869 Cope says : " Further investigation shows that this genus 

 is gavial-like, and that the peculiarity which chai:acterizes its dentition 

 also belongs to Plerodon Meyer, of the European Miocene." 



In 1882 he says, under the head Crocodilus: " A peculiarity of the 

 composition of the crowns of some of the species has been noticed, on 

 account of which I proposed a genus Thecachampsa. In this type the 

 crown is composed of concentric hollow cones, one within the other. 

 I have not been able to separate the crowns of the recent crocodiles into 

 such bodies, and they are generally too thin to display more than a few 

 such layers, were they so separable. This character was first observed 

 in some species of the Atlantic Coast, e. g., C. antiquus Leidy, and C. 

 squankensis Marsh; and the two Eastern Miocene species, C. sericodon 

 Cope (type of Thecachampsa) and C. sicaria Cope." 



