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. 



Produdus Sowerby (Pyxis Chemnitz ; Arlmsculites Murray ; Protonia Linck ; 



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



-?t£a "V 



Fu;. 579. 



A, 

 Same 

 andE 



., Productus semiretiuulatus (^Martm). Lower Carboniferous ; Vise, Belgium, i/,. B, P. 'j/igranieiw (Martin). 



e horizon; England. Interior of dorsal valve (after Woodward). C, D, P. horridus Sow. Permian; Prus.sia 



England, i/j. C, Interior of dorsal valve. Z), Internal mould of ventral valve. ^1, Adductors ; 7.', Diduetors ; 



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



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

 outlines semicircular, sometimes transversely elongate. External surface 



spinose, 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 

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



Produrtmhorridus Sowerby. two deudritic adductors and a pair of broadly flabel- 



Permian ; Gera, Germany. Va- i . ,., r^ t ^ 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. (jiganteus is the largest Brachiopod known, sometimes attaining a width of nearly 

 one foot. 



Subgenera : Diajjhragmus Girty. Produdus with an internal plate in dorsal valve. 

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

 subniargiual ridges. Upper Carboniferous ; Nortli America, India. 



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

 Carboniferous ; India, Russia. 



