128 S. W. Ford—Note on Lingulella celata. 
The surface of both valves is ornamented with moderately 
conspicuous radiating and concentric lines, the latter irregularly 
series alternating with those of the next, and so on, as first 
pointed out by Professor Hall in his description of the dorsal 
valve (Pal. N. Y., vol. i, p. 290, pl. 79, fig. 9). The effect of this 
style of ornamentation is very beautiful ; and when, as is usu- 
ally the case, the shells have a dark, polished aspect, with a 
setting of light-colored limestone, few handsomer fossil objects 
can be named. The shell is thick and of a finely lamellar 
structure. The usual length of the ventral valve is about 
three and one-half lines. 
This is one of the best marked fossils of the Troy Primor- 
dial and may be easily identified by means of very small frag- 
meuts. 
The species known as Obolella crassa of the Troy beds may 
also be briefly noticed in this connection. It includes the 
species already widely known under the name of O. desquamata 
from the same locality, this latter, as may be shown, having been 
founded upon the dorsal valve of the former. The ventral valve 
is always more acutely pointed at the beak than the dorsal, but 
beyond this feature there is nothing, so far as I have been able 
to discover, by which they may be distinguished from each 
other externally. The surface of each, when perfect, is both 
radiately and concentrically striated. As a rule, however, the 
imbricating edges of the successive layers of growth are the 
only markings visible. : 
f the interior of the ventral valve an excellent figure was 
given by Mr. Billings on page 355 of this Journal for May, 1872; 
but the interior markings of the dorsal valve have nowhere, to 
my knowledge, yet been accurately shown. The scars are nearly 
the same with those of the dorsal valve of 0. chromatica,* but 
the smaller pair close to the beak are here, in the majority of 
cases, distinctly connected with the larger pair directly beneath 
them ; while the central pair, instead of running parallel with 
each other throughout, diverge at the mid-length of the valve, 
and extend onward in slender falcate forms into the anterior 
fourth of the shell. Their parallel portions are, however, the 
. only parts usually seen, and it was only after collecting the 
species for a number of years that I obtained evidence that 
what had come to be looked upon as wholes were, in reality, 
only parts of much more extensive impressions. 
The species of Brachiopoda at present known to me from 
the Troy Primordial are the following: Obolella crassa, O. gem- 
*“On the structure of Obolella chromatica,” by E. Billings, F.G.S. This 
Journal, March, 1876. : 
