390 



MOLLUSCOIDEA 



PHYLUM V 



both valves. Ventral valve with small teeth ; dorsal valve with sockets and 



crural plates. Brachial impressions distinct. Devonian ; America and Europe. 



Produäus Sowerby (Pyxis Chemnitz ; Arhusculifes Murray ; Protonia Linck ; 



Producta Sow.) (Figs. 579, 580). Shell without functional pedicle, anchored 



Fig. 579. 



A, Productus semiretimlatus (Martm). Lower Carboniferous ; Vise, Belgium. Vi- B, P.igiganteus(M.a.rtm). 

 Same horizon ; England. Interior of dorsal valve (after Woodward). C, D, P. horridus Sow. Permian ; Prussia 

 and England, i/i- C, Interior of dorsal valve. D, Internal mould of ventral valve. A, Adductors ; R, Diductors ; 

 pr, Cardinal process ; h, Hinge-line ; v, Brachial impressions. 



by the ventral spines ; concavo-convex, valves usually produced anteriorly ; 



outlines semicircular, sometimes transversely elongate. External surface 



spinöse, usually with more or less prominent radiating 



ribs, which are crossed by concentric lines or wrinkles ; 



rarely smooth or finely striated. Cardinal areas, teeth, 



sockets and crural plates absent or rudimentary. 



Ventral valve convex, sometimes geniculated; often 



Fig. 580. with median sinus. Muscular impressions consisting of 



Productus horridus sowerhy. two deudritic adductors and a pair of broadly flabel- 



Permian ; Gera, Germany. 1/4-1 • t -1 /-i t i i 



late, striate diductors. Cardinal process strong, curved 

 or erect, extending far above the hinge-line. Brachial ridges well defined ; 

 traces of spiral or brachial cavities occasionally present in the pallial region. 

 Extraordinarily abundant in Carboniferous and Permian. Distribution 

 general. 



P. giganteus is the largest Brachiopod known, sometimes attaining a width of nearly 

 one foot. 



Subgenera : Diaphragmus Girty. Productus with an internal plate in dorsal valve. 

 Upper Carboniferous ; North America. Marginifera Waagen. Has thickened internal 

 submarginal ridges. Upper Carboniferous ; North America, India. 



Tschernyschewia Stoyanow. Typified by Productus humholdti d'Orb. Upper 

 Carboniferous; India, Russia. 



