Greger — Rare and Imperfectly Known BracMopods. 71 



Art. YI. — Some Rare and Imperfectly Known Brachio- 

 podsfrom the Mississippian ; by Darling K. Greger. 



The four species of Brachiopoda which are figured here 

 have caused not a little confusion to collectors of Mississippian 

 fossils, the writer having frequently observed them severally 

 labeled as the Rhynehonella ringens of Swallow, in local col- 

 lections. That the shell described by Prof. Swallow under 

 the name above referred to may be definitely known, and that 

 a distinctive appellation may be had for the forms long con- 

 fused with it, is the object of the present paper. 



Camarophoria ringens (Swallow). Figs. 7, 8. 



Rhynehonella ringens Swallow, 1860, Trans. Acad. Sci. St. L., Vol. II, 

 page 653. 



Original description. — " Shell large, thick, triangular, pli- 

 cated, truncated and flattened in front. Ventral valve flat- 

 tened, triangular; the anterior and the posterior lateral margins 

 abruptly turned up to meet the dorsal valve : the anterior lat- 

 eral margins curved down in the opposite direction ; beak acu- 

 minate ; sinus wide and shallow, containing about eight 

 plications. Dorsal valve more convex ; anterior and posterior 

 lateral margins abruptly turned down to meet the opposite 

 valve ; strongly arched towards the anterior lateral margins. 

 The juncture of the valves is sharply and deeply serrated. 

 Surface marked with about fourteen large plications on each 

 valve. Length, 1*90 ; breadth, 1*48 ; thickness, 0*99." 



The plications all have their origin at or#near the beak and 

 increase in size as they approach the front, the number occupy- 

 ing the sinus and fold being quite variable ; their number is 

 never increased either by implantation or bifurcation over the 

 body of the shell. 



The specimen we figure is from the Boyce collection and 

 bears a label written by the late Prof. Swallow ; and while it is 

 not so large as the type, we have no reason to doubt its being 

 the species to which his description applies, since we have col- 

 lected from the Burlington cherts of Callaway county numer- 

 ous single valves that equal the dimensions given by the 

 author. Locality and horizon of the figured specimen, and a 

 number of others in our collection — East of New Bloomfield, 

 Callaway county, Mo., in residual cherts of the Burlington 

 limestone. 



That the shell figured by Dr. Girty* from the Madison 



* Monograph U. S. G. S., vol. xxxii, pt. 2, 1899, p. 537, pi. lxix, figs. 1% 

 1\ l e . 



