146 On the Palaeontology of the Coralline Oolites of Oxford. 



rina. The specific term I have chosen refers to the smooth and 

 unornamented surface of the shell. 



Nerincea. — These three species (two from Cumnor and one from 

 Bullingdon) are evidently distinct, but are too imperfect to be 

 identified satisfactorily. 



My best thanks and acknowledgments are due to my friend 

 Dr. Lycett for his most valuable assistance in determining several 

 critical species mentioned in this paper. 



Description of new Species. 

 Placunopsis similis. PI. IX. B. figs. 1, 2. 



Shell ovately orbicular, oblique ; upper valve (the only one known 

 at present) convex ; umbones marginal ; surface covered with 

 dense, very fine, radiating stria?, which are decussated by the 

 lines of growth. 



Locality. Coralline Oolite near Besselsleigh, where it is some- 

 what rare. 



Lima elliptica. PI. IX. B. figs. 3, 4. 



Shell convex, elliptic-ovate, oblique ; centre of the shell covered 

 with acute longitudinal costse, which become nearly obsolete 

 at the sides ; interstices very finely longitudinally striate, as 

 is also the anterior portion of the shell ; auricles unequal (the 

 posterior being the largest) and quite smooth. 



Locality. Coralline Oolite about Bullingdon and the Shotover 

 road; also in the same rock at Pickering, as I am informed 

 by Dr. Lycett. 

 This shell bears a general resemblance to Lima gibbosa, Sow.; 



but that species is not so oblique ; and when minutely examined, 



its sculpture will be found to be very different. 



Modiola Lycetti. PI. IX. B. fig. 5. 

 Shell oblong, concentrically striated, umbones terminal ; dorsal 



surface convex, terminating in a ventricose, bluntly-rounded 



extremity ; inferior border somewhat concave. 

 Locality. This little species occurs sparingly in the Coralline 



Oolite of Bullingdon, and in the quarry near the windmill on 



the Shotover road. 



Ceritella costata. PI. IX. B. fig. 10. 

 Shell turreted ; spire elongated ; whorls flattened, with straight 



longitudinal costs, which, in the body-whorl, only occupy the 



upper part of the volution. 

 Locality. Coralline Oolite near Besselsleigh, but rare. 



Closely allied to Ceritella longiscata, Mor. and Lye. ; but our 

 species wants the keel on the upper part of the volutions (one 



