NATURAL SCIENCES OF PHILADELPHIA. 187 



Genus STENOGYRA, Shuttl. 



I have not been able to examine S. octonoides (S. subula of L. 

 and Frw. Shells, I.) or S. gracillima, but only S. decollata, Lin., 

 from Charleston, 1 S. C, a species introduced from Europe by 

 commerce, and the true S. subula found near Mobile, Ala. Of 

 extralimital species I have examined S. octona, gonostoma, and 

 hasta. Semper has examined S. Panayensis. 



The jaw (see pi. XVI., fig. 1, for that of S. subula) is low, wide, 

 with attenuated, blunt ends, and a wide, slightly produced median 

 projection. There are distinct vertical striae on that of S. 

 decollata. 



The lingual membrane is long and narrow. The central tooth 

 has a very small, high, narrow base of attachment, the lower outer 

 angles generally somewhat expanded. The reflected portion is 

 very small, and bears a short, stout, median cusp, and two very 

 small side cusps ; all the cusps bear distinct cutting points. The 

 lateral teeth are very much larger than the centrals. The base of 

 attachment is about as high as wide, its inner lower lateral expan- 

 sion suppressed as usual. The upper edge is squarely reflected. 

 The reflection is very large, and bears one stout median cusp, 

 extending almost to the lower edge of the base of attachment ; 

 there is also an outer, much smaller side cusp, and a less devel- 

 oped, sometimes subobsolete inner side cusp; all the cusps have 

 distinct cutting points, proportioned to their size ; that on the 

 central cusp being greatly developed. In S. decollata (pi. XV., 

 fig. 5) the inner cutting point is also much developed, and joined 

 to the central cutting point. The marginal teeth in S. decollata 

 are but a modification of the laterals, with the suppression of the 

 inner cusp and cutting point (b) ; the extreme marginals (c) differ 

 in the greater development of the reflected portion and equaliza- 

 tion with it of the cutting points, of which there are but two. In 

 S. subula (pi. XV., fig. 8) the marginal teeth (6) have more nu- 

 merous cutting points, formed by the bifurcation of the inner and 

 outer cutting point. The second denticle from the. inner side is 

 the largest. It will be noticed that in S. decollata both the side 

 cutting points of the laterals are quite thorn-shaped. 



S. decollata, L. (pi. XV., fig. 5, b is one of the first marginals, 



1 I found the species in great numbers at various localities in this city 

 during a recent visit (1875). 



