PALUDINA SUBPURPUREA. 29 



convex whirls, of which the Hnes of growth are 

 very fine and obHque: spire lengthened, with 

 the apex scarcely obtuse: suture well marked: 

 aperture ovate-orbicular, widest in the middle; 

 the posterior end of the labrum is much ad- 

 vanced upon the penultimate whirl: a few in- 

 distinct spiral bands are sometimes visible. 



Color. The tint is difficult to define, but 

 would be approached by a dark shade of 

 Syme's 'brownish purple red' mixed with dark 

 'broccoli brown;' the inside being a lighter tint 

 of the same color. 



Geographical Distribution. Inhabits the 

 Wabash, and some of its branches: Mr. An- 

 thony has received information of its occur- 

 rence near St. Louis, and has sent me a 

 specimen from Wisconsin. 



OBSERVATIONS. 



The tubular cylindrical organ supposed by 

 Say to be a respiratory siphon, is probably the 

 outlet of the viscous glands; but I am not now 

 able to refer to Cuvier's memoir to ascertain 

 the fact. In Paludina decisa it is strongly 

 dotted with orange, and projects forward from 

 the posterior angle of the aperture, at some 



