STENOGYRA. 191 



STENOGYRA, Shuttl. 



Animal : see under Rumina. 



Shell turreted, sometimes truncated, hyaline or white, with a delicate horn- 

 eolored, sometimes reddish epidermis ; whorls straight, numerous, 7-13, gradu- 

 ally enlarging ; apex obtuse ; aperture semioval or ovate-oblong ; peristome 

 straight, generally simple ; columella usually truncated. 



For further details, see under each subgenus. 



I have not been able to examine the jaw or lingual dentition of S. octonoidcs 

 (S. subula of L. & Fr.-W. Shells, I.) or S. gracillima, but only 5. decollata, 

 Lin., from Charleston, South Carolina, a species introduced from Europe by 

 commerce, and the true S. subula found near Mobile, Alabama. Of extra- 

 limital species I have examined S. octona, gonostoma, and hasta. Semper has 

 examined S. Panaycnsis. 



The jaw (see Fig. 9 7 for that of S. subula) is low, wide, with attenuated, 

 blunt ends, and a wide, slightly produced median projection. There are dis- 

 tinct vertical stria; on that of 5. decollata. 



The lingual membrane is long and narrow. The cen- 

 tral tooth has a very small, high, narrow base of attach- lg ' 

 ment, the lower outer angles generally somewhat ex- 

 panded. The reflected portion is very small, and bears 

 a short, stout, median cusp, and two very small side j aw f s. subula. 

 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 expansion 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 developed, sometimes subobsolete inner side cusp ; all the cusps have dis- 

 tinct cutting points, proportioned to their size ; that on the central cusp bein^ 

 greatly developed. In S. decollata (PI. IV. Fig. Q) the inner cutting point is 

 also much developed, and joined to the central cutting point. The marginal 

 teeth in S. decollata (b) are but a modification of the laterals, with the suppres- 

 sion of the inner cusp and cutting point; the extreme marginals (c) differ in 

 the greater development of the reflected portion and equalization with it of the 

 cutting points, of which there are but two. In S. subula (PI. IV. Fig. P) the 

 marginal teeth (b) have more numerous cutting points, formed by the bifurca- 

 tion 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. 



Surgknus RUMINA, Risso. 



Animal hcliciform, blunt before, pointed behind ; mantle posterior, thin, pro- 

 tected by a shell; respiratory and anal orifices on the right of the mantle under 



