296 A. J. JUKES-BROWNE ON THE RELATIONS OF 



the Gault as in the Chalk-marl ; so variable is the shell according to 

 its position and opportunities of growth. 



It must not, however, be confounded with Sowerby's Ostrea cana- 

 liculata (Min. Conch, ii. pi. 135. f. 1), an elongated and slightly cari- 

 nated species, which Mr. Etheridge thinks is probably the same as 

 Ostrea larva (Lam. Anim. sans Vert. vi. p. 216). 



0. vesicularis is a very common shell in the Cambridge nodule- 

 bed, and occurs, as its range would indicate, both as a cast and as a 

 shell, the latter being frequently attached to nodules and boulders. 



ExOGTRA HALIOTOIDEA, SOW. 



Chama (Exogyra) haliotoidea, Sow. Min. Conch, i. p. 67, pi. 25 ; 

 D'Orb. Pal. Er. pi. 478. f. 1-4. 



Eccogyra Rauliniana, D'Orb. Pal. Er. p. 708, pi. 471. f. 1-3 ; Pict. 

 & Camp. Ste.-Croix, pi. 193. f. 15, 16. 



This species has not before been cited from Cambridge; but I 

 possess specimens of very typical form, besides others, undistinguish- 

 able from those so named in the Hunstanton Limestone, which 

 more closely approach the types of E. Rauliniana in shape. Speci- 

 mens undoubtedly belonging to the latter are common at Cambridge ; 

 and I was glad to find, on consulting Mr. Etheridge, that he fully 

 believes them to be only varieties of the same species ; the larger 

 and narrower varieties, usually called E. Rauliniana, are, perhaps, 

 more common in Gault, and wider forms in the higher beds ; but the 

 shape of individuals is so entirely determined by their position of 

 growth that no certain rule is followed. Their favourite station 

 seems to have been upon Ammonites rostratus ; and they frequently 

 bear a perfect cast of the shell on which they grew. 



Lima elongata, Sow. 



Lima elongata, Sow. Min. Conch, pi. 559. f. 2. 



Lima Itieriana, Pict. & Eoux, p. 484, pi. 40. f. 5 ; Pict. and Camp. 

 pi. 166. f. 4, 5. 



This species, which has often been confused with L. parallela, 

 Sow., is the subject of a long discussion by MM. Pictet and Campiche, 

 who finally decide upon abandoning both of Sowerby's names, on the 

 plea of insufficient description and delineation. They range the 

 fossils which have been referred to these species under two heads 

 — Lima Cottaldina, D'Orb., for the Aptian and Lower Greensand 

 species, and L. Itieriana, Pict. and Eoux, for the Gault species ; and 

 they are inclined to regard L. parallela of D'Orbigny as distinct 

 from either. Sowerby's figure of Modiola parallela (M. C. pi. 9. f. 1) 

 is certainly unrecognizable; but I see no reason why his Plagiostoma 

 elongata should not be retained, since its characters are apparent 

 and similar to those of L. Itieriana ; this is the course adopted by 

 Prof. Eenevier in the e Eaune de Cheville,' p. 162. 



? Hinnites Sttjderi, Pict. & Eoux. 



? Hinnites Btuderi, Pict. & Eoux, Gres Yerts, p. 504, pi. 45. f. 1 ; 

 Pict. & Camp. Ste.-Croix, pi. 179. 



