1896. ] NEW YORK ACADEMY OF SCIENCES. 197 
projection at the extremities of the hinge line. The valves 
slope down in all directions to the margin, and the form is so 
symmetrical that it is difficult to ascertain which is the upper 
and which the lower side of the valve; but the side on which an 
obscure marginal fold is found, is supposed to be the lower side. 
It is also difficult to say which is the anterior and which the 
posterior end of the valve; one end has a low tubercle and a 
shallow pit, while the other end is plain; this distinction may be 
used for the purpose of locating the characters of the inner sur- 
face of the test, as seen on the mould of the valve. 
The center of the valve is marked by a distinct circular 
depression, apparently a perforation of the test: from this point 
a faint medium furrow extends toward the tuberculated end, 
where it fades out in the shallow pit existing at that end of the 
valve; this pit is larger than the circular depression at the 
center of the valve, but differs from it in having no defined 
margin; beside this larger pit, but nearer to the margin of the 
valve, is the tubercle above referred to; it is low, somewhat 
pinched up at the sides, and elongated in the direction of the 
larger axis of the valve. The slope of the sides of the valve 
near the margin is nearly vertical, and the marginal fold is very 
feeble and obscure. 
The surface of the valve is granulated, but the granulations 
are more distinct on the inner than the outer surface; the inner 
surface is more brilliant than the outer. 
This Primitia resembles in form and size the Silurian P. tran- 
siens, Bar.; its apparently perforated disc recalls another Bohe- 
mian species, P. perforata, Bar.; in this species the perforation 
and tubercle are situated near the hinge line, but in ours near 
the axis. 
Length, 34 mm.; width, 2 mm. 
Horizon and Locality.—In the conglomerate-limestone band, 
Div. 1.c!, at Porter’s Brook, St. Martin’s. 
In his article on the Olenellus Fauna, of Washington county, 
New York,* Mr. C. D. Walcott has described a peculiar En- 
tomostracan with a flexible test under the name of Leperditia 
(I.) dermatoides with the remark, “ It may be that this species 
should be referred to a new genus.” This fossil resembles one 
which the author has had in his hands for some time, unde- 
scribed. The peculiar wrinkling of the test (under pressure ? ) 
separates these fossils from all other Cambrian Ostracoda, and 
they are here placed in a new genus. 
*Fauna of the ‘‘ Upper Taconic”? of Emmons, in Washington county, N. Y., by C. 
D. Walcott. Am. Jour. Sci., vol. xxxiv., Sept., 1887. 
