198 Trans. Acad. Sci. of St. Louis. 



margin of valve abruptly deflected. Dental lamellae extending- 

 nearly one-third the length of the valve. The beak of this 

 valve projects nearly in the plane of the shell, and the lateral 

 portions of the valve are continued, without convexity, to the 

 borders, thus giving this valve a peculiarly flattened surface — 

 the broad sinus forming a similar plane lying at a lower level." 



The dimensions of the type specimen are: length 17 mm., 

 breadth 27 mm., and convexity of pedicle valve 4 mm. 



Remarks. A single specimen of this species has been 

 observed in the University of Michigan collection, and 

 although it is not marked **type" it is undoubtedly the 

 specimen used by Winchell in his description of the species. 

 It is an imperfect specimen, only a cast of the interior of the 

 pedicle valve being preserved. The species is apparently a 

 member of that group of Rhynchonelloid shells for which 

 Hall and Clarke have used the name Camarotoechia, and it is 

 therefore referred to that genus. It is closely allied to, and 

 is perhaps not specifically distinct from the English species 

 Rhynchonella pleurodon Phill., and from an examination of 

 the illustrations of that species given by Davidson, it seems 

 probable that that author would not have considered the 

 American specimen as a distinct species. The species de- 

 scribed from the Chouteau limestone of Cooper County, Mis- 

 souri, as B. cooperensis Shum. is perhaps not distinct from 

 this Burlington species. 



Spirifer PECULiARis Shum. ? 



PlXX.f. 1. 



A single specimen which may belong to this species has 

 been observed in the fauna under consideration. It is larger 

 than the specimens in bed No. 5 which have been referred to 

 this species, and is also larger than specimens of the species 

 from central Missouri. The specimen also differs from 

 authentic representations of S. pecuUaris in having a well 

 defined cardinal area. This last difference, however, may be 

 due to the state of preservation. 



Spiriferina soLiDiROSTRis (White). 



PL XX. f. 2-4. 



Original description, ** Shell rather small, nearly semi- 

 circular, wider than long, widest at the hinge-line, where it is 



