the cambridge gault and greensand. 291 



Pterocera retusa, Sow. 



Pterocera retusa, Pictet & B,oux, Gres Verts, p. 263, pi. 25. f. 11. 

 Pterocera bicarinata, Desh. ; D'Orb. Pal. Pr. pi. 208. f. 3-5 ; Pictet 

 & Camp. Ste.-Croix, ii. p. 579, pi. 91. f. 5-8. 



Mr. Etheridge informs me that he has no doubt that Pt. retusa, 

 Sow., and Pt. bicarinata, Desh., are really the same species. M. 

 Renevier (Paune de Cheville, p. 142) also considers the specimens 

 figured under the latter name by MM. Pictet & Campiche to be the 

 same as Pt. retusa, though he seems somewhat doubtful about 

 D'Orbigny's Pt. bicarinata. 



A well-marked cast exists in the "Woodwardian Museum, which 

 closely corresponds to those figured from Sainte-Croix. 



Ptjstjs Smithii (Sow.), Pict. and Camp. PI. XIV. figs. 4-6. 



Pyrula Smithii, Sow. Geol. Trans, iv. p. 336, pi. xi. f. 15. 

 ? Fusus Olementinus, D'Orb. pi. 223. f. 8-9 ; Pict. & Camp. Ste.- 

 Croix, p. 640, pi. 95. f. 4, 5. 



Sowerby distinctly says this shell is not the same as his Murex 

 Smithii of the Min. Conch., which has subsequently been trans- 

 ferred to the genus Pyrula, and caused confusion with the present 

 species. Perceiving this, Mr. Seeley, in Ann. & Mag. Nat. Hist. 

 1861, proposed the name of P. Sowerbyi ; but this step is unnecessary, 

 unless the shell is truly a Pyrula ; it has, however, been recognized 

 as Fusus Smithii by MM. Pictet and Campiche ('Ste.-Croix,' summary 

 of the genus Fusus), who remark that it has nearly the same shape 

 as F. Olementinus, D'Orb., but differs by having more numerous ribs. 

 Whether this difference is sufficient to make it a separate species, 

 especially as the Cambridge specimens vary in this respect, I am in- 

 clined to doubt, and should not be surprised if, when a considerable 

 series of specimens come to be compared, they should be found to pass 

 into one another. Mr. Price possesses two specimens of F. Clemen- 

 tinus from the Lower Gault of Polkestone. 



Natica Clementina, D'Orb. 



Natica Clementina, D'Orb. Terr. Cre't. ii. p. 154, pi. 172. f. 4. 

 Natica ervyna, Pict. & Eoux, Gr. Verts, pi. 17. f. 2 (non D'Orb. ?). 

 Turbo rotundatus, Sow. Min. Conch, pi. 433. f. 2. 



M. Renevier has worked out the above synonymy and published it 

 in a note contributed to the Societe Vaudoise des Sciences Natu- 

 relles for 1856. He comes to the conclusion that the N. ervyna of 

 Pict. & Roux, but not D'Orbigny's original figure, is identical with 

 N. Clementina, which, again, he believes to be the shell named Turbo 

 rotundatus by Sowerby. He therefore calls the shell Natica rotun- 

 data ; but this leads to such confusion with N. laevigata, Desh., which 

 Forbes called N. rotundata, thinking it was Sowerby's Turbo rotun- 

 datus, that it appears better to drop Sowerby's name altogether, and 

 take D'Orbigny's, by which the species is best known. It is charac- 

 teristic of Lower Gault, and is very rare at Cambridge, 



Q.J.G.S, No. 122. x 



