234 
PALEONTOLOGY OF NEW YORK. 
Diagnosis. Shells with a subsemicircular marginal outline; convex or 
subpyramidal in the typical group. Hinge-line straight, and forming the 
greatest diameter of the shell. Pedicle-valve elevated, cardinal area high, ver¬ 
tical, or sometimes incurved, and crossed by a broad delthyrium, which is 
normally covered by a convex, perforate deltidium. On the interior of the 
valve the dental lamellae are very strongly developed, converging and uniting 
in the median line before reaching the bottom of the valve; thus forming a 
spondylium* which with the deltidium encloses a conical subrostral vault. 
This plate is supported by a median septum extending for about one-half the 
length of the valve. Muscular impressions obscure. In the brachial valve, the 
cardinal area is considerably developed, and the delthyrium filled by a con¬ 
spicuous callosity, against the inner side of which the simple orthoid cardinal 
process abuts. The dental sockets are large, the crural plates low and continu¬ 
ous with the edges of the delthyrial callosity. A thickened transverse area is 
formed in the umbonal region by the union of the inner portions of the crural 
plates with the cardinal process, and thence a broad median ridge is continued 
forward through the muscular area, which is sharply defined and quadripartite. 
External surface covered with radiating striae. Shell-substance impunctate. 
Type, Pronites adscendens , Pander. Lower Silurian. 
American example, Orthisina Verneuili, von Eichwald. Trenton limestone. 
Observations. Although d’Orbigny’s term, Orthisina, has found its way 
into general use for this group of shells, there is no reason why it should replace 
the name Clitambonites, a genus clearly defined and abundantly illustrated by 
its author. In order to show Pander’s conception of this group, and since his 
“ Beitrage zur Geognosie des russischen Reiches ” is a work not generally ac¬ 
cessible to American students, his original descriptions and typical figures are 
here introduced.! 
* 27 rovdvXlov, vertebra'. This term will apply with equal propriety to the similar plate existing in 
pedicle-valve of other brachiopods, e. g., Clitambonites, Pentamerus, Camarella, STEN0SCHiSMA(-etc^^ 
f Pander’s determinations of genera and species of brachiopoda evince a remarkable insight and ana¬ 
lytical power. He was in this regard a generation in advance of his contemporaries, who apparently felt it 
their duty to throw both his genera and species back into the old groups whence they were derived, and 
thus totally ignore his work. The inaccessibility of Pander’s works to western students, has been one great 
cause of the misunderstanding of many brachiopodous genera. 
