126 ANNALS NEW YORE ACADEMY OF SCIENCES 



•ent on the ventral than on the dorsal valve, on which they are often evanescent 

 about the margins for a greater or less distance. They vary considerably in 

 different specimens, being more closely arranged in some than in others, 

 occurring from nine to eleven in 3 mm. They also vary on the same specimen 

 in proportion to their distance from the apex, and are more crowded on the 

 posterior than on the anterior side ; consequently, the measurement given 

 above is a relative one, representing the condition toward the front in well- 

 grown specimens. Exfoliation obliterates much of the concentric marking and 

 instead often brings to view fine radial lines and stria?, probably due to seta? 

 which projected from the margin of the shell. 



On the interior, the dorsal valve has a short septum passing longitudinally 

 through the apex, and extending farther on the anterior than the posterior side 

 of it. There are also two symmetrical ridges, straight, parallel and close 

 together for some distance anterior to the apex, rapidly diverging and some- 

 what curved near it, so as partly to surround it. Between the straight ex- 

 tended anterior portion of these arms there is a medium groove which extends 

 backward and graduates into the septum, which has depressed sides. The 

 curved arm-like markings probably represent the boundary of a line of muscu- 

 lar attachment. In one specimen these lines are, near the apex, distinctly 

 expanded into oval areas, one on each side, each of which is separated by an 

 oblique line of division into two scars. These areas, without much question. 

 are the loci of pairs of muscles. 



The internal markings of the dorsal valve described above are conspic- 

 uous on most of the specimens examined, which are usually preserved as 

 internal molds. They vary in detail in different examples. This pecu- 

 liar structure seems to be identical with that upon which Hall and Clarke 

 based the subgenus Rcemerella, and while there may be a little doubt as 

 to whether it is really of subgeneric value, it will, together with the con- 

 figuration, readily distinguish this form from other Pennsjdvanian dis- 

 cinoids. Some specimens, especially if incompletely exfoliated, fail to 

 show this structure, however. 



Rcemerella patula is rather abundant in the Wewoka formation and 

 usually occurs as dissociated valves in small concretions. Occasionally, 

 however, the two valves are found in conjunction, though usually more 

 or less displaced. 



Horizon and locality : Wewoka formation ; Wewoka quadrangle, Coal- 

 gate quadrangle, Okla. 



Streptorhynchus oklahomae sp. nov. 



There are in the Wewoka collection two specimens which appear to belong to 

 the genus Streptorhynchus. They are preserved as internal molds and show 

 dental callosities in the ventral valve without any trace of a septum. In the 

 dorsal valve, the socket plates are fairly well developed and one specimen has 

 a low dorsal septum. In point of convexity the dorsal valve is only gently 



