NOTES ON THE CAMBRIDGE GREENLAND. 499
of these ridges. There are very few striated Naticce known from Cretaceous beds ; and this appears to differ from all of them. The above description is from a specimen in the national collection, from the Gault of Folkestone. It has the shell partially preserved ; but where this is absent a cast is disclosed of the same shape and dimen- sions as those from the Cambridge bed (fig. 6), which in my previous paper (p. 292) I provisionally referred to N. Rauliniana, D'Orb.
Nerita nodulosa, new sp. PI. XXI. figs. 7, 8.
Shell very thick ; spire depressed ; whorls angulated and flattened above, ornamented when young with numerous small ribs, which proceed from the spire and, passing over the head, run vertically for a short way down the side of the whorls ; they are then broken up into small nodules or tubercles. As the shell increases in growth, however, the upper parts of the ribs also become nodulose, so that near the mouth the ornamentation is entirely changed ; large, irregular, nodulose tubercles are developed on the keel, apparently by the union of two or three ribs ; and above each, on the flat portion of the whorl, are two smaller nodules. At the same time the outer lip is enlarged, flattened, and applied against the inner whorls, somewhat as in recent Neritce.
A single specimen only is known, in the cabinet of J. Carter, Esq. Length about 13 lines, breadth 9 lines, height unknown ; and the lower part of this is broken away, so that the characters of the base cannot be ascertained.
Although the fossil above described is unique and imperfect, yet so much of the original thick shell is retained ; and this is so remarkable in its shape and ornamentation that I have thought some account of it might be published.
At the same time I have had great difficulty in deciding to what genus it probably belongs. It might almost be referred to Strapa- rollus, or Euomphalus ; but the angle which the outer lip makes with the inner whorl is greater than in these genera, and leads to the conclusion that the last whorl was considerably produced below. This is the case with a shell named Nerita rugosa by MM. Briart and Cornet (Meule de Bracquegnies, pi. iii. figs. 50-52), which the Cambridge fossil appears to much resemble in shape and general features.
N. rugosa has thick, radiating ribs of a uniform character, each ending in a nodular projection at the keel, below which the shell is smooth ; the base is not umbilicated ; it is thus specifically different, though it appears to be generically identical. Whether, however, they are true Neritce some doubt may be entertained.
Pleurotomaria regina, Pict. & Rx.
Pleurotomaria regina, Pict. & Roux, Gres Verts, pi. xxiv. fig. 2.
Casts of this species are among the fossils from the Perte du Rhone recently placed in the Woodwardian Museum ; and from them I have been able to identify certain low, closely whorled
