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, impunctate.” 
The type of this genus is the little Productus lamellosus, Sandberger,* which is 
conceded to be synonymous with Schnur’s Terebratula venusta-\ from the middle 
Devonian of the Eifel. From Schnur’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. kpida, 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 Vei'steinerungen des rheinischen Schichtensystems in Nassau, pi. xxxiv. iig. 18. 1850-1856. 
t Zusammenstellung und Beschreibung samnitlicher im Uebergangsgebirge der Eifel vorkommenden 
Bracbiopoden, p. 180, pi. xxiv, fig. 3, a. b. 1853. 
