362 Mr. W. Clark on the Littorinidse. 



a minute orifice ; the female is oviparous ; the antepenultimate 

 whorls are always flat in this species, being a condition resulting 

 from the shape and size of the ovarium, which is only adapted 

 for ova ; it is however much more prolific than the Littorina rudis 

 and varieties. 



This is the common edible periwinkle of the London markets, 

 and the only one, as the females of the L. rudis and all its va- 

 rieties are viviparous, and cannot be used for food in consequence 

 of the grittiness arising from craunching the testaceous pulli ; it 

 is found in all situations often exposed to the full influences of 

 an open sea, but more usually in estuaries and muddy inlets, 

 which are also the habitats of certain varieties of the L. rudis ; it 

 grows to li inch in length and i inch diameter. 



Littorina rudis ^ Donovan. 



L. tenehrosa^ L. zonaria, L. rudissima, L. juyosa, "j 



L. patula, L. nefflecta, L. fahalis, L. saxatilis, and, >auctorum. 

 sub fide Forbesii, L. palliata, &c., J 



This well-marked species has nearly the same organs as L, lit- 

 torea ; I have compared the nervous ganglions and other internal 

 parts of both forms, without finding distinction. To enumerate the 

 greater part of the other organs, in comparison with those of L. 

 littorea, Avould be a repetition ; I will only mention the essential 

 specific distinction, which is, that in the females of this species 

 the large bulky ovarium is usually filled with strings of testaceous 

 pulli ; that is, if they are examined at the season when, ! Alma 

 Venus, thy votaries are '^perculsse corde tua vi,^^ the ovaries 

 fill up the tumid antepenultimate volutions. The markings and 

 colours of the animal have the same character as those of Litto— 

 rina littorea, except that they are much less intense ; but though 

 closely allied, it is very particularly distinguished by the much 

 higher littoral level of its habitat, the greater tumidity of the 

 volutions, colour, and above all by the very diff'erent ovarium, its 

 contents and mode of reproduction. It rarely exceeds an inch in 

 length and three-quarters of an inch in diameter. 



To describe the varieties enumerated above, which are the 

 pseudo-species of authors, would be to say, that the organs of all, 

 both internal and external, do not vary in the slightest degree 

 in form ; the only diff'erences are modifications of colour, size, and 

 in the striae, depending entirely on habitat. The L. rudis, L. tene- 

 hrosa, L. zonaria and L. rudissima are usually inhabitants of the 

 estuaries and muddy oozes, and rarely exposed to the full action 

 of an open sea. 



We earnestly recommend naturalists in their respective loca- 

 lities to consign the four species above-named to basins of water, 

 together with all the dwarf varieties inhabiting the crevices of 



