324 PROCEEDINGS OF THE NATIONAL \llsi:i\l. vol.38. 



The scutes of the plastron (Plate 12, fig. 2) have a remarkable 

 arrangement. On cadi bridge are two inframarginals, an anterior 

 and a posterior. The anals and the femorals can be identified with- 

 out doubt. The femorals extend forward to the byo-hypoplastral 

 suture. In front of the femorals is a pair of large scutes thai reach 

 nearly the middle of the entoplastron and overlap the hinder ends 

 of the epiplastron. On each side, lying between the scutes just 

 described and the inframarginals, is another large scute that extends 

 from the axillary to the inguinal notch and inwardly to within about 

 18 mm. of the midline. It seems that these last-mentioned scutes 

 must be the abdominals which, as in Chelydra, have been crowded 

 from the midline by the expansion of the pectorals and the femorals. 

 There are no traoes of intergulars. Gulars and humerals remain 

 to be accounted for, and only a single pair remains. It seems prob- 

 able that the gulars have been suppressed or have coalesced with the 

 humerals. The arrangement of the plastral scutes of this genus 

 resembles that of Baptemys tricarinata, a except that the abdominals 

 of Hoplochelys have been excluded from the midline. 



This species differs from //. crassa (Cope) in having the lateral 

 keels of the carapace broader and more obtuse. //. crassa also 

 evidently had the abdominal scutes pushed away from the midline. 

 The width of these at the inguinal notch was aboul 13 mm.; whereas, 

 in //. bicarinata, a larger individual, these scutes are only 5 mm. wide. 



From //. csdata b the present species differs in not having the bones 

 sculptured with oblique ridges. The outer faces of the hinder 

 peripherals are not flat, as they are in Il.csdata, but more or less 

 concave, with the free borders somewhat upturned. In Il.csdata 

 the hypoplastron did not enter the eighth peripheral. The hinder 

 end of the seventh is thin, as is also the whole of the eighth. In 

 //. bicarinata the anterior end of the eighth is much thickened and 

 receives a process from the hypoplastron. The hypoplastron of 

 //. crassa (Cope) does not pass behind the seventh peripheral, resem- 

 bling in this respect //. cselata. 



ASPIDERETES AMNIGENUS, new species 



The writer ventures to describe as a new species a trionychid 

 turtle which was secured by the same party that discovered the type 

 of Basilemys prseclara and in the same locality and formation. The 

 catalogue number in the U. S. National Museum is 6574. This turtle 

 is represented by the greater pari of one costal plate (Plafe LI, fig. I . 

 which appears to be the second of the left side. Of this costal 

 there is presenl all except a small portion near the middle of the 



"llay. Fysil TurtleB of North A.merica, p. 276, figs. 347,348. 

 MLiy, Proc. V. S. Nat. Mtm vol 35, p. L63, pi. 27. 



