220 
PALEONTOLOGY OF NEW YORK. 
cretion retains two plates in juxtaposition, one of which indicates that the true 
form was sub-conical, appressed at the sides, with a broadly rounded, somewhat 
flattened dorsum. The anterior margins, from the apex to the base, appear to 
have been distant, leaving a broad cleft between them. Some of these charac¬ 
ters are also shown upon the flattened specimens. There is but one exception 
exhibited to the general sub-triangular form of these plates, and that is afforded 
by a small example in which the apex is central and both anterior and poste¬ 
rior margins convex. The substance of the valves is chitinous, tenuous and 
reduced to a carbonaceous film; the surface is ornamented by concentric undu¬ 
lating ridges, which are closely crowded near the apex, and also near the basal 
margin in old specimens. The dorsum shows traces also of fine elevated 
radiating lines. 
These plates vary in size from a length of 6 mm. and a height of 5 mm. to 
a length of 27 mm. and a height of 20 mm. Fragments also indicate a very 
much greater size. 
Observations. The fossils which constitute this species vary widely in some 
features from those referred to Plumulites by M. Barrande, as well as from other 
species of this genus occurring in the rocks of New York State. All these 
are of very much smaller size, and are simple plates, never folded or rounded 
over the back or conical, and are usually characterized by a conspicuous ridge 
passing from the apex to near the basal margin. It is difficult to see how the 
combination of these sub-conical bodies in vertical ranges could produce such a 
scaly peduncle or capitulum as existed in Turrilepas. Should the anterior mar¬ 
gins of these valves prove to be cleft from apex to base, they will resemble 
much more closely in form, contour and surface sculpture, the fossils which 
have been described under the genus Spathiocaris (page 199). 
Distribution. In the black shales at Sheffield and Birmingham, Erie county, 
Ohio. In Mr. Whitfield’s description the fossils were referred to the “ Huron 
shale,” equivalent to the Genesee shales and the lower portion of the Portage 
shales of New York; Dr. J. S. Newberry has however, in corrected labels upon 
the specimens, referred them to the “ Cleveland shale,” the uppermost Devon¬ 
ian strata of Ohio. 
