130 PALEONTOLOGY OF NEW YORK. . 



" The dorsal valve is not very concave ; its little cardinal process is divided, 

 and is bordered on each side by a stout lamella, outside of these lying the deeply 

 excavated dental sockets ; to these lamellae the two depressed spiral cones, 

 with their many volutions, appear to be united ; both cones having the same 

 position as in Koninckina [ ? J. Beneath the cardinal process, and on either side 

 of a thick median septum, lies a broad, oval impression of the adductor muscle, 

 which is divided by a more or less prominently developed oblique ridge ; from 

 the upper and lower margins of this impression originate the vascular sinuses 

 which are directed toward the edges of the valve. A small, round, deep im- 

 pression beneath the cardinal process is, at present, not understood ; it lies at 

 the spot where presumably the curvature of the alimentary canal occurred. 

 Shell-structure fibrous, irapunctate." 



The type of this genus is the little Produdus lamellosus, Sandberger,* which is 

 conceded to be synonymous with Schnur's Terehratula venustaf from the middle 

 Devonian of the Eifel. From Schnor's description of the species we derive a 

 more detailed account of the external sculpture of the shell than that given by 

 Sandberger and Suess. 



The shell is small, concavo-, or plano-convex, with incurved umbo, open, or 

 but partially closed delthyrium and no cardinal area. 



" On the pedicle-valve is a narrow median groove separating two broadly 

 rounded plications which bifurcate near their origin at the beak, and disappear 

 near the middle of the valve ; on each lateral slope are three additional and 

 smaller plications which also disappear before reaching the anterior half of the 

 shell. There is a faint plication in the median sinus. Both plications and 

 sinuses are crossed by closely set, imbricating concentric growth-lines, which 

 make the surface quite rough, more so than in T. lepida, which the shell very 

 closely resembles." 



This species has not received the careful study it requires in order to eluci- 

 date some of its critical features. Sandberger's description and figures are, 

 nevertheless, excellent, and the more important of these have been here intro- 

 duced. The structure of the loop is still unknown. The spirals were coiled 



* Die Veisteinerungen des rheinischen Schichtensystems in Nassau, pi. xxxiv. fig. 18. 1850-1856. 

 t Zusammenstellung' und Beschreibung- sammtlicher im Uebergangegebii-ge der Eifel vorkommenden 

 Brachioiioden, p. 180, pi. xxiv, fig. 3, a. b. 1853. 



