324 
PALAEONTOLOGY OF NEW YORK. 
frequently scattered irregularly over the surface, generally strongest and dis¬ 
posed with greatest regularity upon the cardinal extremities, and sometimes oc¬ 
curring only in this region. They are hollow and appear to have communicated 
with the interior cavity of the shell. On the interior of the valve is a narrow 
median ridge, separating the two dendritic impressions of the adductor muscles; 
outside and in front of these are two broadly flabellate, longitudinally striated 
scars of the cardinal muscles. In the pallial region are sometimes found traces 
of spiral cavities, which were occupied by the fleshy arms.* 
The brachial valve is operculiform, more or less concave or almost flat over 
the visceral area. Cardinal area, sockets and crural plates absent or rudi¬ 
mentary ; 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 longitudinal septum, dividing the impressions of the adductor 
muscles. The latter are strongly dendritic and rarely divisible into anterior 
and posterior elements. The brachial ridgesf take their origin from near the 
post-lateral margins and nearly enclose a sub-circular, smooth or granulose 
area. The internal surface of this valve is strongly postulose, and in the 
pallial region frequently spinous. 
* See Davidson, British Carboniferous Brachiopoda, pi. xxxvii, fig. l. lSbl. 
f Waagen says (Productus-limestone Fossils, p. 611): “A passage in Professor Neumayr’s paper 
[Neues Jahrbuch fur Mineralogie, 1883, vol. ii, p. 27], which is of very great importance, I must quote here 
more in detail. He says, a chief objection of Davidson’s against the opinion that these ridges form a part 
of the brachial apparatus is the existence of spiral impressions which are to be found in the ventral valve 
of some specimens of Productus, and which beyond any doubt are impressions of the spirally enrolled arms 
of the animal. Now, as these impressions show not the slightest accordance with the brachial ridges [reni- 
form impressions], Mr. Davidson concludes that these latter cannot be taken as belonging to the brachial ap¬ 
paratus. ‘ I cannot concur,’ says Professor Neumayr, ‘in this argument. The greatest number of the now 
living Brachiopods have arms showing a double curve ; and if such were, as is probable, present in Pro¬ 
ductus, these features (the ridges in the one and the spiral impressions in the other valve) are in no way 
difficult to explain ; on the contrary they indicate very accurately the direction and the manner in which the 
arms extended in Productus. They run first along the descending, then along the reascending branch of 
the ridges, were then bent back over the descending branch, and curled in a spiral coil, which caused the 
impression in the ventral valve. Thus, in their general shape, these arms very nearly agree with those 
occurring in Terebratula and Waldheimia, though in proportion and direction of the different parts certain 
differences exist.’ This deduction is of very great systematic importance.” 
