460 MISSISSIPPIAN BBACHIOPODA 



from the point of greatest convexity to the lateral and anterior margins 

 and more abruptly to the cardinal margin ; mesial fold obsolete ; the beak 

 only moderately incurved beneath that of the opposite valve, but not ex- 

 tending as far posteriorly; internally the valve bears a median septum 

 which reaches from the beak anteriorly to or a little beyond the middle 

 of the valve, from each side of this septum, at approximately one-half 

 its height, a horizontal plate is developed whose distal margins for a 

 distance of one-third or less the length of the median septum, rests 

 against the inner surface of the valve, the two plates together forming 

 an elevated platform for muscular attachment, which is excavated be- 

 neath, the excavation being divided longitudinally by the median septum. 

 In the internal casts of the valve, as they usually occur, the two finger-like 

 casts of this excavation are usually broken off ; on each side of the median 

 septum the surface of the internal casts of the brachial valve is often 

 marked by radiating vascular sinuses similar to those of the opposite 

 valve and not reaching the anterior margin of the shell. 



The surface markings of the shell are unknown, but the shell was 

 probably smooth or marked only by concentric lines of growth. 



Remarks. This species is known only in the form of internal casts 

 from the higher, yellow sandstone of the Kinderhook at Burlington, Iowa, 

 and is usually in the condition of casts of separate valves. When the 

 species was made the type of the genus Camarophorella by Hall and Clarke, 

 the shell was supposed to be one of the Pentameridse, but specimens of a 

 closely related species from the "Waverly at Sciotoville, Ohio, have re- 

 cently been shown by Hyde 1 to be spire-bearing, and to belong among 

 the meristelloid forms. No indication of spiral appendages have been 

 detected in the Burlington specimens, but in light of the evidence fur- 

 nished by 'the Sciotoville specimens there can be no doubt but that such 

 appendages were present in the living shells. This Kinderhook species 

 differs from the Sciotoville form, C. mutabilis Hyde, in its smaller size and 

 in the absence of a median fold and sinus. 



Horizon. Kinderhook. 



CAMAROPHORELLA MISSOURIENSIS (Winchell) 

 Plate LXXXII, Figs. 70-79 



1865. Spirigera Missouriensis Winchell, Proc. Acad. Nat. Sci. Phil., p. 117. 

 1908. Seminula bucMeyi Rowley, Mo. Bureau Geol. and Mines, vol. 8, 2nd 

 ser., p. 79, pi. 17, figs. 48-53. 



Description. Shell below medium size, longer than wide or wider than 

 long, subovate to subpentagonal in outline. The dimensions of the holo- 

 type are : length of pedicle valve 16.9 mm., length of brachial valve 14.8 



iProc. Boston Soc. Nat. Hist., vol. 34, pp. 35-65 (1908). 



