220 
PALEONTOLOGY OF NEW YORK. 
from the Black River limestone of the Ottawa river; a very similar shell is 
the C. Panderi, described at the same time from the same locality ; indeed, there 
may be reason to doubt if there is a valid specific difference in these shells, as 
both the Canadian specimens and examples from the Trenton limestone of New 
York (Jacksonburg), afford a series passing from the typical plicated form of one 
to the non-plicated form of the other. 
Camarella Volborthi has full, convex valves, which are smooth about the um- 
bonal region, but anteriorly develop a few low plications which are rather the 
more conspicuous on the median fold and sinus, and the fold, sinus and plica¬ 
tions are clearly developed on the often abrupt anterior slope of the valves. 
The pedicle-valve is the more convex up to maturity, but thereafter the 
brachial valve becomes the deeper. The beak of the pedicle-valve is erect or 
slightly incurved and beneath it lies a triangular delthyrium which, so far as 
observed, shows, neither in this species nor in C. Panderi, any evidence of del- 
tidial plates. The cardinal slopes are abrupt and oblique, and no cardinal area 
is developed on either valve. On the interior are dental lamellas which con¬ 
verge, and uniting, are supported by a short median septum, forming thus a 
well-defined spondylium like that of Synteophia. 
In the brachial valve the hinge-structure is similar to that of Camarotcechia, 
the crural plates converging and forming a short, very small median cavity, 
which is supported by a long septum. The crura are short and the lateral 
divisions of the hinge-plate small. No cardinal process exists. 
The internal structure of Camarella is, thus, not unlike that of Syntrophia, 
notwithstanding the wide difference of exterior. 
Many American species have been referred to this genus, but, from present 
knowledge it would seem to be quite restricted in range and specific representa¬ 
tion. Apparently it does not pass beyond the faunas of the Lower Silurian, 
and it is probable that most of the species referred to the genus by Mr. Billings 
will prove to have been accurately placed, though in regard to some of them, 
their rarity and unfavorable preservation make it impossible to be positive. 
The species Camarella ? antiquata, Billings, from the early primordial faunas, may 
or may not belong here; we know it only from the figures of the exterior 
