NATURAL SCIENCES OF PHILADELPHIA. 183 



and bears a short, stout, median cusp, having a short, blunt, 

 cutting point. There are no side cusps or cutting points. 



The laterals b are like the centrals, but unsymmetrical; their 

 reflected portion is also longer. The outer laterals (e) have an 

 outer side cusp. 



The marginals d are a simple modification of the laterals, being 

 quadrate, longer than wide, with one inner broad, long, oblique, 

 bluntly pointed cutting point, bearing an inner, side, short, acute 

 cutting point. These cutting points on the extreme marginals e 

 are simply short and bluntly rounded. 



Some membranes examined by me seemed to have an extension 

 to the base of attachment beyond the upper margin of the reflected 

 portion, to which it was parallel. 



This membrane is peculiar in the long, narrow base of attach- 

 ment and short reflected portion of the central and first lateral 

 teeth. 



Genus HOLOSPIRA, Mart. & Alb. 



There are two species of this genus found within our limits, 

 H. Goldfussi and fioemeri, the former of which I have been able 

 to examine. I have not been able to examine lingual mem- 

 brane of H. Roemeri, but, thanks to Mr. Bland, I have examined 

 and here figure (pi. XX., fig. 10) that of H. Goldfussi. There are 

 26 1 26 teeth, with about 9 laterals. The cusps of the marginals 

 are quite widely separated. The general characters of the teeth are 

 as described below. I can refer also to Messrs. Fischer and Crosse 

 for information regarding the jaw and dentition (Journ. de Conch. 

 XVIII. 13, 1870, pi. V., and Moll. Mex. et Gnat., 320, pi. XVI.) 

 The jaw is arcuate, with slighly acuminated, blunt ends, thin, 

 anterior surface ribless ; cutting edge simple; transversely and 

 vertically striated. 



The lingual membrane in 77. Tryoni and Pfeifferi examined 

 and figured by those authors, is of the usual Helicinse type. The 

 centrals and laterals have a single short cusp, bearing a short, 

 blunt cutting point, both side cusps and side cutting points being 

 absent ; marginal teeth quadrate, wide, low, with one long, inner, 

 obtuse cutting point, and one outer, side, short, blunt cutting 

 point. 



