GASTEROPODA OF THE LOWER GREEN MARLS. l39 



sharp, but close; aperture^ (as shown on the only specimen in hand, which 

 is a matrix containing the shell of one side of the specimen in place and 

 from which a gutta-percha cast is taken for description and figure), is 

 round, but the margin is not preserved; surface of the shell marked by 

 oblique varices, which have a slightly backward direction in crossing 

 from the upper to the lower side of the volution; the varices are thin and 

 recurved, and number eight on one-half of the circumference of the last 

 volution, but decrease somewhat in number toward the apex of the spire; 

 axis imperforate, the base of the last volution bordered by a raised carina, 

 below which the varices do not appear to extend. So far as can be ascer- 

 tained from the specimen, I should judge that the varices were slightly 

 produced in the upper part to form subspiues around the base of the pre- 

 ceding volution. The minute surface character of the shell can not be ascer- 

 tained from the specimen in use, as only the inside of the substance is 

 revealed, but Dr. Morton describes it as marked by "very minute spiral 

 striae," which one would suppose would naturally be the case. Mr. Grabb 

 also speaks of it having "much finer" revolving striae than his Scala {Opalia) 

 Thomasi, which is also a New Jersey species, and says that "each rib is 

 reflected back into a little lip or notch at the angle of the basal carina." 



This is readily distinguished from S. annulata Morton, by the more 

 slender spire and by being a very much smaller shell, with an imper- 

 forate axis, that one having a wide, open umbilicus. The shell has so 

 exactly the form, taper, size, and style of varices as 8. Sillimani as given 

 by Dr. Morton, that I have not hesitated to identify it with that species, 

 although the type of it was an Alabama shell. I have not seen specimens 

 of S. Sillimani from Alabama in a good state of preservation, however, 

 and may be in error. 



Formation and locality: In the Lower Grreen Marl near Holmdel. Col- 

 lected by the Rev. Dr. Reiley. Dr. Morton's specimens were from Prairie 

 Bluff, Alabama, but this specimen certainly can not be distinct from the 

 one figured by Dr. Morton. 



