162 KANSAS UNIVERSITY SCIENCE BULLETIN. 



very distinctly posteriorly, and the beak appears to be situated 

 farther back. 



These shells differ from the known Pleurophori in the pos- 

 session of ^^^orisma-like "granulations" below the beak, 

 which seem to be accompanied by the vaulting at this place 

 of the lamellse of growth. The granulations are roughly ar- 

 ranged in radiating rows. This shell has, so far as may be 

 determined from the material at hand, the external characters 

 of Pleurophorella Girty. However, he allies that genus with 

 Allorisma, as a probable subgenus. Our specimens are cer- 

 tainly closely similar to Pleurophorus in dentition, muscular 

 markings, and form. If Girty's genus is closely related to 

 Allorisma, as he thinks it is, we cannot refer our specimens to 

 it. If parallel development is to be looked for among the 

 pelecypods, where it seems to me to be very likely to occur, 

 external features are of little value as generic criteria when 

 the critical characters are unknown. At any rate, the Dozier 

 and Whitehorse specimens cannot be referred, even provi- 

 sionally, to Pleurophorella until Doctor Girty determines 

 whether it belongs in the order Anomalodesmacea or the order 

 Teleod^smacea. 



Our specimens differ from the Pleurophori only in the pos- 

 session of granulations on the region beneath the beak and 

 perhaps a reduction of the upper cardinal tooth. 



PLEUROPHORUS ALBEQUUS LONGUS, n. var. 



Plate VI, figure 9. 



More than three times as long as high, hinge usually 

 straight, umbonal ridge very faint. Dentition as in the pre- 

 ceding species. Some of the valves show angulation on the 

 posterior end just below the hinge line. No definite radia- 

 ting ridges seen on adult specimens, though they may be 

 present, as the larger the specimen the more poorly it is 

 preserved in these rocks. The depression beneath the beak 

 appears to be missing and the ridge back of the adductor im- 

 pression is nearly vertical. Otherwise as in the species. 

 Two specimens : Length, 27 mm, 13 mm. ; height, 7 mm, 4 

 mm., respectively. 



Whitehorse spring, Oklahoma; common. Dozier, Tex.; 

 rare. 



