614 Forty-fifth Report on the State Museum. 



The brachial valve is operculiform, more or less [concave or 

 almost flat over the visceral area. Cardinal area, sockets and 

 crural plates absent or rudimentary; cardinal process strong, 

 curved or erect, extending far above the hinge-line ; its inner face 

 is divided into two lobes by a longitudinal furrow, and each of 

 these parts is deeply divided at its extremity, giving the process 

 in this aspect a quadrilobed appearance. As viewed from the 

 posterior or outer face it is strongly trilobed, the inner members 

 of the lateral lobes coalescing to form a very prominent apophysis. 

 The process is continued over the interior of the shell as a longi- 

 tudinal septum, dividing the impressions of the adductor muscles. 

 The latter are strongly dendritic and rarely divisible into 

 anterior and posterior elements. The brachial ridges take their 

 origin from near the post-lateral margins and nearly inclose a 

 sub-circular, smooth or granulose area. The internal surface of 

 this valve is strongly pustulose, and in the pallial region fre- 

 quently spinous. Shell substance fibrous, strongly punctate. 



Type, Productus semireticulatus, Martin (sp.). 



Distribution. Devonian (?) — Permian. 



Subgenus Productella, Hall. 1867. 

 (Plate 21, Figs. 15-24.) 



Shells small, productoid. Surface spinous. Pedicle-valve with 

 narrow cardinal area, deltidium and small teeth. Brachial valve 

 with sockets and crural plates. 



(Type, P. suhaculeatus, Murchison (sp.). Devonian.) 



Subgenus Marginifera, Waagen. 1884. 

 (Plate 22, Figs. 13-15.) 



Externally like Productus. On the interior of the pedicle- valve 

 are prominent shelf-like ridges on either side of the beak, extend- 

 ing inward and crenulated on their margins. There are similar 

 but vertical ridges on the interior of the brachial valve. 



(Type, Marginifera typica, Waagen. Devonian (?) to Permian.) 



Subgenus Proboscidella, (Khlert. 1887. 



Valves very unequal; the brachial valve small, concave, oper- 

 culiform; the pedicle-valve Larger, convex, furnished with two 

 Lateral expansions which bend downward to meet tin 4 margins of 



160 



