DERMATEMYDID^I. 



275 



shown in the figure. His rig. 4 represents the second left peripheral. Fig. 8 is from a portion 

 of the left first costal and its median notch fits accurately on the upper border of the original of 

 his fig. 4. Cope's fig. 6 is almost certainly that of the right third peripheral. In the collection 

 there are present the left second and third peripherals of another individual. These bones cer- 

 tainly do not belong to any species of Baena. They closely resemble those of Baptemys wyo- 

 mingensis, and in all probability belong to that species. 



Cope's assignment of these bones to Baena was determined by the bone represented by 

 his fig. 3. It is indeed very peculiar. Fig. 345 represents a section. Cope regarded it as form- 



FlGS. 342-345. Baptemys wyomingensis. Pelvis, scapula and peripheral. 



342. Pelvis, from left side. Xjf. No. 5934 A. M. N. H. il, ilium; isch, ischium; pub, pubis. 



543. Pelvis of individual of fig. 342. Seen from below. X. il, ilium; isch, ischium; pub, pubis. The suture 



between the right and left pubes ran from a point 2 mm. on the left of the leader from pub backward to 



a point 2 mm. on the left of the line of two short dashes. 



344. Scapula. Xj. Specimen in U. S. N. M. 



345. Section of peripheral described by Cope as that of Baena ponderosa. Xi- 



ing a part of the hinder border of the carapace, the scute seen on it being the hindermost 

 one. However, the writer has found in the collection another fragment which continues the 

 border 5 or 6 mm. toward the left, and on it begins another marginal scute. It is the writer's 

 conclusion that this bone also belongs to Baptemys and is a malformed portion of the hinder 

 border of the carapace. 



Baptemys tricarinata sp. nov. 

 Figs. 346-349- 

 Dermatemys , Cope, Bull. U. S. Geol. and Geog. Surv. Terrs., VI, 1881, p. 184. 



Remains belonging to 2 individuals of the present species were collected in the Wind 

 River deposits, during the summer of 1905, by the expedition in charge of Mr. Walter Granger, 

 of the American Museum of Natural History. One of these, No. 6109, was found at the 

 mouth of Alkali Creek, Fremont County, Wyoming; the other, No. 61 10, on the divide 

 between Alkali and Poison Creeks. No. 6109 is made the type of the species. Both specimens 

 are considerably fractured, neither of them furnishing a complete carapace. Taken together, 

 however, the two specimens give practically the whole structure of the shell. The species is 

 distinguisht from B. wyomingensis by the possession of three dorsal carina? and a pointed 

 hinder plastral lobe. 



The carapace of No. 6109 (fig. 346) has. an approximate length of 460 mm.; a width of 

 about 330 mm. Its structure differs only in minor points from that of B. wyomingensis. The 

 neurals are long and narrow. The peripherals differ little from those of the Bridger species, 



