LITTORINA. 367 



UddevaUa (J. G. J.). They inhabit both sides of the 

 Atlantic, from Spitzbergen (Torell) to Lisbon (M f An- 

 drew) in the eastern hemisphere, and from Hamilton's 

 Inlet (Wallich) to Massachusetts (Say) in the western 

 hemisphere. Kutorga has enumerated L. rudis as a 

 South-Crimean species, and Mr. Lord has brought home 

 specimens from Vancouver's Isle. 



Lister distinguished this from the common eatable 

 periwinkle by the name of Nerita reticulatus } &c. ; it 

 was figured by Chemnitz as a variety of the former 

 species. Schroter seems to have mistaken it for a fresh- 

 water shell. I have taken it in places overflowed by 

 streams during the recess of the tide, together with the 

 common mussel and limpet. There are three distinct 

 forms, resulting from a difference of habitat. One of 

 them lives among loose stones and pebbles on the beach ; 

 another on mud ; and the third on rocks, 



" And all along the indented coast 

 Bespattered with the salt sea foam." 



These forms have given birth to a multiplication of 

 species, the details of which fill, but do not improve 

 every book and treatise on our native mollusca. " 'Tis 

 sixty years since " the viviparous habit of L. rudis was 

 noticed by Boys*. It seems to breed throughout the 

 whole of the summer. Mr. Bate observed couples en- 

 gaged in procreation while the females contained not 

 only eggs in every stage of development, but perfectly 

 formed young, which were about to enter on their own 

 separate errand of life. According to Dr. Johnston this 

 function is continued far on in November, both in the 

 present species and L. obtusata. The male is, as usual, 

 smaller, and has a longer spire. It may be presumed 



* Mr. Eich has enabled me to add Clausilia biplicata, and probably 

 C. ruffosa and Balia perversa, to the list of viviparous mollusca. 



