GASTBEOPODA OP THE LOWER GREEN MARLS. 133 



cies when placed together being very distmct. It is very closely related 

 to A. paludincBformis, Natica paludinceformis, H. & M., having a much greater 

 resemblance to it than the one herein described as A. Meekana, although 

 that one has been commonly identified with it. This has probably arisen 

 partially from the fact that this one, having originally been described 

 under the name Phasianella, was so far removed systematically from the . 

 Naticidse, to which it really belongs, that it would scarcely be thought 

 necessary to compare them, or even occur to one to do so. 



Formation and locality: In the lower layers of the Lower Green Marls, 

 at MuUica Hill. New Jersey. Collection Acad. Nat. Sci., Phila. 



TROCHID^. 



Genus MARGARITA Leach. 



Margarita abyssina. 



Plate XVII, Figs. 1-5. 



Solarium abyssina Gabb : Proc. Acad. Nat. Sci. , Phila. , 1860, p. 94, PI. ii, Fig. 9. 

 Architectonica abyssina Gabb : Synopsis, pp. 39, 80. 



Margarita abyssina (Gabb) Meek: Check List Cret. and Jur. Foss., p. 18; Geol. 

 N. J., Newark, p. 728. 



Shell small, not exceeding half an. inch, in its greatest diameter; spire 

 moderately elevated, the apical angle being about 70° or 75°; volutions 

 four to four and a half, very ventricose, giving a circular section when 

 broken across; suture deep and well marked, while the whorls in the inter- 

 nal cast are closely appressed and slightly imbedded into each other, show- 

 ing the shell to be thin; also seen where the cast rests partially in the 

 matrix, the space left by the removal of the shell where no compression 

 has occurred being barely perceptible ; umbilicus broad and open, showing 

 several of the volutions within; surface marked by very fine, even, spiral 

 lines over the entire shell, with an apparent stronger line on the periphery, 

 and crossed by finer lines of growth which are bent backward in crossing 

 the volution, cancellating the surface. 



In Mr. Gabb's original description the surface structure was not given, 

 as he had not been able to find more than the internal cast, but among the 



