MOLLUSCA. 745 



surface of the shell have been determined from plaster casts taken 

 from natural moulds of the shell, of which several incomplete ones 

 have been studied. The species is especially characterized by the 

 strong and deep sutural furrow or fossula, and the strong revolv- 

 ing costae. A careful comparison of the specimens in the recent 

 collections with Gabb's original examples, the figured type and 

 two others, has shown that their identification is correct. Gabb's 

 specimens were all internal casts, so that the remarkable sutural 

 groove is not shown upon them. The sharply defined collumellar 

 fold, indicated in Gabb's original illustration of the species, does 

 not exist in the specimen. Different individuals of the species 

 vary somewhat in the height of the volutions, but the abrupt con- 

 traction to the anterior canal is characteristic. The large 

 individual illustrated by Whitfield is not this species, and is prob- 

 ably not a New Jersey specimen. The internal casts of this 

 species seem to resemble the one illustrated by Whitfield as P. 

 perlata more closely than any other, and it is quite possible that 

 that specimen, which certainly is not P. perlata Con., may belong 

 to P. septemlirata. It differs from most of the specimens chiefly 

 in the greater angularity of the periphery. The exact number of 

 revolving costse upon the surface of the shell has not been deter- 

 mined with certainty, indeed there is probably some slight varia- 

 tion in the number in different individuals, and in all the speci- 

 mens observed they seem to have been eroded or otherwise 

 destroyed except towards the aperture. 



The type of Whitfield's P. corrina seems to be only a rather 

 smooth internal cast of this species, but not smoother than is 

 frequently met with. 



Formation and locality. Navesink marl, Atlantic Highlands 

 (108), MullicaHill (169), Holmdel (Whitfield). 



Geographic distribution. New Jersey. 



Pyropsis planimarginata (Whitfield). 

 Plate LXXXVL, Figs. 11-14. 



1892. Tudicla planimarginata Whitf. Pal. N. J., vol. 2 (Monog. 

 U. S. G. $., vol. 18), p. 33, pi. i, fig. 1-3. 



