510 S. WELLER — MISSISSIPPIAN RHYNCHONELLIFORM SHELLS 



It agrees with that species in the absence of a brachial median septum, 

 in the short dental lamellae of the pedicle valve, and in the presence of a 

 median, longitudinal depression, in the nmbonal portion of the brachial 

 valve. 



Camarotgechia Hall and Clarke 



general characteristics 



In the Devonian faunas of North America the genus Camarotcechia 

 has an abundant representation. The members of the genus are charac- 

 terized by the presence of a median septum in the brachial valve which is 

 divided internally to form a short crural cavity between the two sides of 

 the divided hinge-plate. The crural cavity is commonly very short, 

 sometimes terminating posterior to the articulation of the valves, but the 

 simple, unattached median septum sometimes continues with gradually 

 diminishing height, well toward the center of the valve. In the pedicle 

 valve members of this genus are supplied with well developed dental 

 lamellae which join the floor of the valve independently. In their exter- 

 nal configuration members of the genus Camarotcechia are strongly and 

 more or less angularly plicated, the plications continuing to the beak, and 

 they possess a well defined fold and sinus. 



CAMAROTCECHIA CHOUTEAUENSIS N. SP. 



In the Mississippian faunas a single well defined but undescribed spe- 

 cies of Camarotcechia has been observed. It is a common form in the 



•? s 8 8 8 a Q Q 



Figure 10. — Cross-sections of the rostral Portion of Gamarotoechia chouteauensis n. sp. 



This series of eight cross-sections (X 2i/^) is from a specimen from the Chouteau lime- 

 stone of central Missouri 



Chouteau limestone and may be called C. chouteauensis. A series of 

 cross-sections of the species is shown in figure 10. 



WiLSONIA KaYSER 

 WILSONIA GR08VEN0RI (HALL) 



A species which was referred to the genus Pugnax by Hall and Clarke 

 and by Schuchert is Rhynchonella grosvenori Hall. Internally this spe- 

 cies possesses all the essential characters of Camarotoechia, as is shown in 



