S. W. Ford—Note on Lingulella celata. 127 
jority of the species, not rising above the surface of the fixed 
eks. The entire surface is covered witha fine regular gran- 
ulation. 
This species is the second one of the genus, so far as I am 
aware, that has been described from American rocks, the first 
one having been obtained from strata of the Acadian epoch 
in Newfoundland and described by Mr. Billings. It occurs in 
both even-bedded and conglomerate limestone of the Lower 
otsdam group at Troy, N. Y., associated with Olenellus, Cono- 
coryphe and Microdiscus. It is principally interesting on account 
of its affording another generic link between the already 
closely related faunz of the Acadian and Lower Potsdam. 
New York, Oct. 13th, 1877. 
Art. XVIL—Note on Lingulella celata ; by S. W. Forp. 
THE above mentioned species, occurring in the Troy Pri- 
mordial, has hitherto been set down by me as an Obviella, but 
the evidence now in hand shows tbat it should be referred to 
the genus Lingulella of Salter. The following are the principal 
characters : 
The ventral valve is somewhat elongate-ovate, with the beak 
pointed, slightly elevated and conspicuously channeled for the 
peeeee of the pedicle. The convexity is moderate and nearly 
position the large lateral scars of the ventral valve of certain 
species of Obolelia (e. g., O. chromatica.) The other impressions 
of this valve have not been made out. 
The dorsal valve is more rotund than the ventral and has the 
beak much depressed. The convexity increases with increas- 
ing age, and in adult specimens is such as to sometimes give 
the valve a semi-globose appearance. A shallow depression 
extends in all the specimens from the beak to the front margin, 
but in fully grown forms it is often inconspicuous. On the 
inside there are four prominent ridges. Of these the more cen- 
tral twocommence close to the median line a short distance in — 
front of the beak and extend into the forward third of the 
shell slightly diverging throughout, while the lateral pair take 
their rise close to the beak and reach to points a little in ad- 
vance of the mid-length. There is also a short slender ridge 
directly beneath the beak on the median line. The central por- 
tion of the valve in the upper half is slightly excavated. The 
description of the interior of this valve has been mainly drawn 
up from an excellent natural internal moul 
