372 LITTORINID^. 



convexity; in the middle one each transverse range 

 contains several, which are small and nearly square. 

 All are too minute to be distinguished, except under a 

 high magnifying power. The magnified lingual mem- 

 brane appears beautifully reticulated." And he further 

 remarks that the periwinkle " feeds upon the softest 

 algae. I have observed it devouring a minute filament, 

 which entered the mouth by a succession of jerks, re- 

 peated at very short intervals. In this case it is pro- 

 bable that the filament passes undivided into the 

 stomach. When browsing upon larger fragments, the 

 portions cut away are so very small that the impressions 

 left can be seen only by a close inspection." M. Beu- 

 dant's celebrated experiments show that the present 

 species has a greater capability than L. obtusata of 

 living in fresh water. There was probably some mistake 

 in the assertion of Bouchard-Chantereaux that the pre- 

 sent species is viviparous, like L. rudis. Although this 

 peculiarity may have been wrongly attributed by him to 

 L. litorea, instead of to a variety of the last-named spe- 

 cies, the particulars which he gives are sufficiently in- 

 teresting to justify their being transferred to these 

 pages, and they are as follows. The female produces 

 about 600 young ones, which are clustered in a vascular 

 ovary, situate on the upper part of the body, and ex- 

 tending from the liver to the right tentacle where the 

 orifice or duct lies ; the fry are expelled one by one 

 during a period of many hours in succession, so that 

 about six or seven months elapse before the entire birth 

 is completed ; the growth of the year's brood is there- 

 fore very unequal, the first born being eight or ten times 

 the size of the last. This statement that the common 

 periwinkle is viviparous seems to be disproved by the 

 fact that it is eatable at all seasons of the year and is 



