350 PALEOZOIC PALEONTOLOGY. 
RHIPIDOMELLA OBLATA (Hall). 
Plate XLVI., Figs. 5-7. 
See, also, p. 304, pl. XXXYV. 
In the middle zone of the New Jersey Oriskany, associated with 
Orbiculoidea jervensis, Metaplasia plicata, &c., there occurs some- 
what commonly a large species of Rhipidomella which seems to be 
identical in all respects with the Helderbergian FP. oblata. 
RHYNCHONELLA BREVIPLICATA Ni. Sp. : 
Plate XLVI., Figs. 2-4. 
Description.—Shell subcircular, slightly wider than long. Pedicle 
valve convex, depressed towards the front in a shallow, mesial sinus, 
which is produced anteriorly into a lingual extension at nearly right 
angles to the plane of the valve; cardinal margins abruptly inflected, 
slightly concave, forming an angle of about 90° at the beak; beak 
acute, not strongly incurved. Brachial valve much more strongly 
convex than the pedicle; elevated toward the front in a low, mesial 
fold. Surface of both valves smooth posteriorly or marked only by 
very fine, indistinct, radiating lines; towards the margin there are 
about three rounded plications on each side of the fold and sinus, and 
three or four in the sinus, which become obsolete very quickly as they 
extend back from the margin. 
The dimensions of a pedicle valve are: length, 13 mm.; width, 14 
mm.; those of a somewhat larger brachial valve are: length, 15 mm. ; 
width, 17.5 mm.; convexity, 6 mm. 
Remarks.—This species is strikingly different from any of the con- 
temporaneous Rhnychonelloid shells, and resembles, in its lack of 
plications except near the margin, some of the much younger 
Paleozoic species referred to the genus Pugnaz. In some respects 
it resembles some species of Eatonia, especially H. peculiaris and #. 
singularis, but the fine radiating lines are much less conspicuous than 
on those species, as they can scarcely be detected save with a lens. 
The inflected cardinal margin of the pedicle valve is ike Eatonia, but 
the valve has not the flatness of that of the described species of that 
