72 PALEONTOLOGY OF NEW JEESEY. 



The following species which we have referred to this new genus is 

 less strongly marked in its generic features than the types, but is sufficiently 

 strongly marked when seen in good specimens of even small size to be at 

 once separable from either Avicula on the one hand or Melegrina on the 

 other, and if we must take the features of the typical species of Oxytoma as 

 the standard, it certainly cannot belong to that genus, as Meek suggests it 

 probably is, in his Invert. Pal. U. S. Geol. Surv. Terrii, page 35. 



Meleagrinella abrupta. 



Plate XIV, Figs. 11-14. 



Avicula abrupta Con. J. A. N. Sci., Phil., Vol. IT, 2d ser., Vol. II, p. 274, PI. IV, Figs. 

 5 and 6. 



Shell small, inequivalve, rhombo-quadrate in outline, the hinge-line 

 long and straight, reaching nearly the entire length of the shell, beaks 

 small, situated at about the anterior third or fourth of the length of the 

 hinge; that of the left valve rising a little above the cardinal line, and that 

 of the right just to its margin. Riglit valve with a deep notch-like slit on 

 the anterior side just below the hinge, with a narrow, deep groove running 

 from it to the apex of the valve on the exterior surface. Left valve provided 

 with an internal fold, quite indistinct' except under a glass, on the anterior 

 side of the beak, which corresponds to the byssal notch of the right valve. 

 Anterior margin of the valve somewhat regularly rounded; basal margin 

 broadly rounded, and the posterior obliquely tru-iicate, passing backward 

 slightly from the hinge extremity to the postero-basal line. Surface of the 

 valves smooth or very finely lamellose, and marked with concentric undul^e. 

 When not at all worn or macerated the surface of the left valve shows 

 indistinct thread-like, interrupted, radiating lines which remind one very 

 strongly of those seen on species of Placunojnya. 



In Mr. Conrad's original description of tliis shell he refers it to Avicula^ 

 but in general appearance it resembles more nearly the common pearl 

 oysters Meleagrina, On more critical examination it is seen to possess the 

 features of the Jurassic shells Eumicrotis ciirta, and E, orbiculata, which I 

 have made the types of a new genus, Meleagrinella^ on account of the peculiar 

 features of the byssal notch, in which they differ from Meleagrina, although 

 more nearh^ related to that than to those of any other established genus. 



