BIVALVIA. 67 
Dogger, the Gray Limestone, the Cornbrash, the Kelloway Rock, and the Coral Rag ; 
numerous specimens are also in the Tessonian collection from Normandy, now in the 
British Museum. Some of these examples are almost destitute of the posterior angle, and 
approach so nearly in the general figure to Sowerbya crassa, D’Orb. = Isodonta Des- 
haysea, Buv., that they might fairly have been assigned to that species, if we had not the 
assurance of M. Buvignier that his specimens from two localities are in a good state of 
preservation, and that they are destitute of ornamentation—a feature which is always dis- 
coverable in good examples of 8. friangularis, whether British or Foreign. 
Mr. Whiteaves has figured a small species of Sowerbya, ‘ Aun. and Mag., Nat. Hist.,’ 
August, 186], under the name of S. ¢riangularis, Phil. Having had the advantage of 
comparing the original specimen, through the kindness of Mr. Whiteaves, with various 
Yorkshire specimens of S. ¢riangularis, I feel unable to coincide in the opinion that it is 
identical with the species of Professor Phillips; the new Oxfordshire form is much 
smaller, less inflated, destitute of ornamentation ; and the posterior side is so short that 
‘ truncata’ would be an appropriate name: it is from the Coral Rag of Oxfordshire. I 
have also found it in the Calcareous Grit at Scarborough Castle. 
The second small species figured by Mr. Whiteaves upon the same plate under the 
name of S. Deshaysca, Buv.? also appears to be distinct from each of the foregoing 
examples; the general figure is more compressed, the anterior slope is excavated, 
which renders its lower extremity pointed; the whole aspect somewhat resembles a 
Nucula. 
Our specimen figured is from the Cornbrash of Scarborough, 
Sowrrsya Woopwarpl, Zyc. PI. XU, figs. 27, 27 a, 27 6, 27. 
Testa ovato-trigona subdepressa, subequilatera, latere posteriore breviori, planata, 
levigata angulo obliquo diviso, dorso et latere antico striis longitudinalibus regularibus 
crebris, delicate instructis. 
Shell ovately trigonal, rather depressed, subequilateral, the posterior side being the 
shorter ; the umbones are not very prominent nor large; the anterior and posterior borders 
slope obliquely downwards ; the extremities of the valves are rounded; the surface has 
delicate, closely arranged regular longitudinal or concentric striations, which are separated 
from the smooth and flattened posterior side by a distinct angle. 
It is much smaller, more depressed, more lengthened, and the umbones are much less 
elevated than in S. friangularis, Our right hand figure is imperfect at the posterior 
extremity, and the posterior oblique angle is not clearly shown; the left hand figure 
has the anterior extremity too obtusely rounded, the specimen wanting a little of its 
border. 
Geological Position and Locality, The Great Oolite of Bussage, near to Bisley 
