14: 



very gentl}^ arched or broadly rounded ; basal margin concave in the 

 middle and convex behind ; anterior end obliqnel}' subtruncate below 



the beakn, narrowest towards the base; posterior extremity ? 



beaks terminal, obtuse. The test happens to Ije removed from the hinge 

 area, and on the cast the superior border of both valves is obtusely 

 carinate, each keel having a concave groove along its inner face. 

 These carinti) and grooves extend the whole length of the hinge, and 

 define an elongated, lanceolate, escutcheon-like depression. 



Surface marked l)y close set, and regular, raised, concentric striations 



Estimated length of the most perfect example, about three inches and 

 two lines; actual height, in the middle, one inch and tAvo lines; maxi- 

 mum convexity, one inch and four lines. 



There are two specimens of this species, one of which has most of the 

 thin test preserved on the left valve, though not on the right, while the 

 beaks and a small piece of the posterior end are broken oft'. The other 

 consists only of the anterior half of a cast of both valves, with a very 

 small fragment of the test attached; but this specimen shows the shape 

 and position of the beaks. The muscular and pallia! impressions are not 

 visible in either. 



In Modiola major of G-abb,* the beaks are not terminal, and the surface 

 is marked by coai-se, distant and irregular lines of growth, but the 

 general shape of that shell is otherwise very like that of the present 

 fossil. Although pi-obably new to science, the two mutilated specimens 

 yet obtained ai'e insufficient to show the full characters of the species. 

 If the generic name Vohella of Scopoli is, as some writers assei't, exactly 

 synonymous with Modiolu, Lamarck, the farmer name has long priority. 

 The point being still somewhat doubtful, it has been thought best to 

 retain a name sanctioned by long usage. 



AucELLA MosQUENSis ? Von Buch. 

 Plate X., figfr'. 3, 3rt. 



For the synonymy of Europeaul examples of this species, see Eijhwald's " Letlisea 

 Rossica," Vol. II., pp. 519, 520. 



Probably ^ Aucella Piochii Gabb. " Pahvontology of California," Vol. 1., page 187, 

 Plate XXV., fig. 173, and Vol. II., pages 194 and 247, Plate XXXII, figs. 92, a. h. <: 



Shell moderately convex, obliquely obovate, narrowest in the umbonal 

 region. Anterior side very short, somewhat truncated ; posterior side 



' " Palaeontology of California," Vol. II., page 191 Plate XXXI., fig. 88 



