much larger and sharper in the English species. If these variations 

 with the differences in color and the three lateral tentacles instead of 

 four constitute good specific differences, then the name alabaslrum 

 should be retained. I think, however, these differences should be 

 considered geographical variations. 



SKENEA PLANORBIS Fabricius 

 PI. III. Fig. 12. Diameter 2mm. 



This is next to the smallest gasteropod on our coast, the smallest 

 being Homalogyra atomus, which I discovered at Hampton beach and 

 which afterwards was found in Rhode Island, by Miss M. W. Brooks, 

 recorded in the "Nautilus," (Vol. XXIII, No. 6). The animal of 

 Skenea is very active and bold. It is found under stones between 

 high and low water mark and also on sea weeds. Accustomed as it 

 is to the thrashing about of the weeds by the dashing waves it becomes 

 hardened to bufifiting and hence its bold behavior. It is found on 

 both sides the Atlantic. The animal is brownish in color. Forbes 

 and Hanley describe the English species as hyaline white. The shell 

 figured by them is certainly larger than that of the American species. 

 In our species the shell is carried erect as in the figure and not resting 

 flatways as described by Jeffreys. Further comparisons may show 

 that our species is different from the European one. 



RISSOA MINUTA Totten 

 PL III. Fig. 13. Length 4 mm. 



Professor Cleveland, of Cornell, long since dead, collected this 

 species in the Charles River estuary in great numbers and soon detected 

 a form somewhat more globose which he considered another species 

 and intended to describe it under the name of Rissoa pigmenla. When 

 he told me that he noticed a marked difference in the odor of the 

 two forms I realized that the difference was sexual, and the form was 

 probably that of the female of the species. It is strongly pigmented, 

 the pigmentation being the result of some minute algae growing on the 



