76 FOSSIL TURTLES OF NORTH AMERICA. 



The second vertebral scute is 90 mm. long in the midline, and is 72 mm. wide across its 

 middle. Similarly, the third scute is 87 mm. long and 72 mm. wide; the fourth, 75 mm. long, 

 deeply concave behind, and 75 mm. wide. The fifth scute is 35 mm. long and 100 mm. wide. 

 Its posterior edge comes to the border of" the shell, there being no supracaudal. 



The anterior marginals are somewhat damaged. In tront there is a nuchal scute 30 mm. 

 from side to side and 16 mm. fore and aft. On the right side there are 2 small marginals, 

 each about 15 mm. long. On the left side there is 1, perhaps 2, corresponding marginals. Then 

 follows, on each side, a marginal about 44 mm. long, succeeded by several others of about 

 the same or greater length. Further behind they shorten gradually, and the last one is very 

 small. The first long marginal has a height of 20 mm. at its middle; the majority of them 

 have a height of about 38 mm. Further behind the height is less. 



The sulcus running along the midline of the plastron pursues a very irregular course, and 

 the same is true of some of the others. That behind the gulars runs from the midline 

 outward and backward for half its length, thence forward and outward. That defining the 

 intergulars does not, at the midline, quite reach the one behind the gulars. The pectorals are 

 about 87 mm. wide at the midline; the abdominals about 35 mm. 



The sulcus between the femorals and the anals is extremely irregular. The right 

 femoral at the midline is 62 mm. wide, the left, 78 mm. wide. There are four inframar- 

 ginal scutes. The first, or axillary, is 58 mm. long and 40 mm. wide; the second has the form 

 of a trapezium, with outer and hinder borders each about 40 mm.; the third is four-sided, 

 50 mm. long, 60 mm. wide. The inguinal scute is pentagonal, about 46 mm. long and broad. 



A second specimen belonging apparently to this species, No. 5957 of the American Museum, 

 was collected in the Bridger beds in 1903. It has the first vertebral scute symmetrical, 43 mm. 

 wide in front, 65 mm. wide posteriorly. There is on each side of it a triangular super- 

 numerary costal scute. 



From B. arenosa the present species differs in displaying with considerable distinctness 

 the sutures between the various bones. In no specimens of B. arenosa that have hitherto been 

 collected have the sutures of the carapace been observed. It is unlikely that this disappearance 

 of the sutures is due to greater age of the specimens of B. arenosa. Furthermore, the cara- 

 pace of B. arenosa has a quite elaborate sculpturing along the middle of the back. Of this 

 B. clara shows only the merest suggestions. The rear of B. clara is scallopt, but the cuts 

 are much shallower than in the other species. The vertebral scutes of B. clara are narrower 

 than those of B. arenosa. However, the most striking differences between B. clara and the two 

 species above mentioned are found in the shape of the shell. The outline of B. clara is oval. 

 The widest part is across the middle of the length and from this the border curves gracefully 

 toward the front and rear. In B. arenosa the outline is somewhat quadrate. The sides are 

 approximately parallel as far back as the rear of the plastron; then the border turns abruptly 

 toward the midline. 



Baena riparia sp. nov. 

 Plates 17, 18; plate 19, figs. 1-3; text-figs. 59-66. 

 Baena arenosa, Cope, Vert. Tert. Form. West, 1884, p. 148, plate xvii, figs. I, 2 (not of Leidy). 



Baena riparia has as its type a fine shell and skeleton, a prize of the American Museum 

 expedition of 1903 into the Bridger deposits of southwestern Wyoming. It was found at the 

 Grizzly Buttes, about 15 miles southeast of Fort Bridger. The beds belong to those designated 

 as B. The specimen is in the American Museum of Natural History and has the number 5977. 



The carapace (plate 17; text-fig. 59) of this specimen is slightly crusht on the left side 

 and the hindermost peripherals are mostly gone; otherwise the shell is complete. The cara- 

 pace is especially valuable because the bones are not co-ossified, and practically all the 

 elements may be determined. It has an axial length of about 315 mm., a slight dislocation of 

 the bones of the rear making the estimate inexact. The width is 260 mm. From the middle 

 of the length the width decreases gradually to the somewhat projecting front. The rear has a 

 wide but shallow sinus over the tail. In fig. 59 the outline of the rear behind the eighth periph- 

 eral to near the pygal is somewhat conjectural, but must be close to the real condition. 

 Along the middle of the back there runs a distinct channel which extends out beyond the 

 neural bones. Along the middle of this there is seen a narrow ridge, on each side of which 



