458 MISSISSIPPIAN BRACHIOPODA 



of the mesial fold of the brachial valve. It differs from, N. rowleyi in its 

 larger size, its thicker and more elongate shell. 

 Horizon. Lower Burlington white chert. 



Genus CAMAROPHORELLA Hall and Clarke 



Description. Shells small or of medium size, subcircular, subovate or 

 transversely subelliptical in outline, the valves subequally convex, a fold 

 and sinus present or absent but never strongly developed. Surface of 

 the shell nearly smooth, marked only by fine concentric lines of growth 

 and sometimes by very obscure radiating stria?. The pedicle valve with 

 the beak moderately incurved, perforated by a rather large, subcircular 

 foramen which encroaches upon the umbo, the delthyrlum closed by 

 deltidial plates. Internally the dental plates are well developed, they 

 unite before reaching the floor of the valve to form a spondylium which 

 is supported by a median septum which is as long or longer than the 

 spondylium and reaches to about the middle of the valve. In the brachial 

 valve there is a strong median septum extending one-half the length 

 of the valve, which supports the hinge-plate posteriorly; throughout the 

 length of this septum there is a transverse platform which originates 

 beneath the hinge-plate, and which is penetrated by and attached to the 

 septum, at its lateral margins this platform curves towards the floor of 

 the valve and is attached to it, forming a cavity between it and the 

 inner surface of the valve which is divided longitudinally by the median 

 septum, to this platform the adductor muscles were attached. The hinge- 

 plate is deeply concave ; the long and slightly curved crura are continua- 

 tions of this plate, being inserted on its sides near the anterior margin ; 

 the spiral cones consist of eight or ten volutions each, the primary 

 lamellae being united posterior to the middle of the jugum, which rests 

 upon the high median septum, it is saddle-shaped, somewhat similar to the 

 condition in Atliyris, but much smaller, the accessory lamellae are placed at 

 a sharp angle to each other, the outer portions lying just without and 

 parallel to the primary lamella?, they recurve and are attached to the 

 jugum near its base. 



Remarks. This genus was originally described by Hall and Clarke 1 as 

 a near ally of CamaropJioria because of the well-defined spondylium in 

 the pedicle valve supported by a median septum, associated with the 

 median septum in the brachial valve. It has been shown by Hyde, 2 

 however, that these shells are spire-bearing with a brachidium of atheroid 

 type. The platform developed in the brachial valve for muscular attach- 

 ment simulates the cruralium in the same valve in Camarophoria, but the 

 lateral margins of the platform curve in the opposite direction from the 



1 Pal. N. Y., vol. 8, pt. 2, p. 215. (1894.) 



2Proc. Boston Soc. Nat. Hist., vol. 34, No. 3, pp. 35-65(1908). 



