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 



