On some Paloiozoic Ostracoda. — Jones. 339 
shales from the Marcellus limestone of Perry county, Penn- 
sylvania (near New Bloomfield). There are several, and they 
vary from 1 to 2| mm. in length. The proportions of some of 
the best are given in the figures 10-13, magnified fifteen diam 
eters. In some respects thej' resemble Bollia lata Hall ;■* but 
they are larger, and the central curved ridge is much thinner 
at its curve, whereas in the specimens from New York state 
the cui've is thicker just there, and is not so symmetrical 
throughout as in the Pennsylvania specimens. Hence I pre- 
fer to regard the latter as specifically distinct, and to adopt 
Prof. Claypole's MS. specific name (having reference to the 
hoof -like ridge), than to refer them to Bollia lata. A hollow 
cast of the outside, and one presumably perfect valve give 
evidence of a smooth exterior. 
The slight variations in the shape and proportions of the 
curved subcentral ridge and of the n>arginal ridge are well 
shown in the figures 10-13. 
5. PRIMITIAPENNSYLVANICA. Sp. nOV. FigS. 15a, 15b. 
Another small ostracod, 1 mm, occurs in the buff-shale of 
the Marcellus limestone, from Perry county. Pa. Related to 
Primitia mundula* Jones, ("Ann. Mag. Nat. Hist." ser. 2. 
vol. XVI (1855), p. 174, pi. 6, figs. 28 to 31), it is, however, 
much more oval than any there figured. The dorsal is even 
more arched than the ventral margin, and curves downwards 
anteriorly more rapidly than it does behind. The sulcus, 
well defined, and bordered on each side by a distinct swelling, 
is much nearer to one end than the other of the valve, not 
quite at its highest convexity, but very near the greatest curve 
of the dorsal edge. 
Note on a specimen of oolitic limestone from the Marcellus series Perry 
county. Pa., which accompanied the foregoing specimens. By Edward 
Wktiiered, Esq., F.G.S., F.C.S., &c., &c. 
When seen as a liand specimen, this rock pfomised well for an 
interestin.ii microscopic sliiie. Oolitic granules were clearly defined; 
but the anticipations as to well preserved structure were not realized. 
The rock was soft to grind, and a certain amount of cleavage was 
apparent. The sect'ons showed the oolitic granules in an argillaceous 
matrix, with very minute grains of detiital material. The granules 
showed the usual concentric structure, but there was an absence of a 
nucleus, which in the British Jurassic ool.tes and Carboniferous oolitic 
limestone is a feature. The granules are ferruginous ; 1 rather suspect, 
* Pahvontolngy of New York, vol. ii, 1.^52, p. SOI, pi. A G6, figs. 
10a, b, d (not tigs, c and e), also some in the British museum. I may 
here mention that I have to refer lata and symmetrica to Bollia, and 
spinosa to zEchmina. 
