LITrOEINA. 147 



species as given by those authors, in a summary at the end 



of their more particular descriptions and more numerous 



divisions. 



L. Neritoides assembles in great numbers very high up on 

 the shore ; sometimes so very high that the tide can 

 scarcely reach it, and where it caii only be occasionally 

 washed by the spray. It is small ; it has a black head 

 and snout, and a white band in front of the foot. 

 The shell is smooth, conical, with the mouth rather 

 spread out in front; its colour is very dark, nearly 

 black, occasionally relieved by a white band. 



L. littorea: the common Periwinkle as described above. 

 It is oviparous. 



L. nulls is viviparous, the ovaria being found in the autumn 

 full of comj)letely-formed young shells. It is of a 

 lighter hue than L. littorea, without the linear arrange- 

 ment of the colours. The shell is smaller, more rugged, 

 with a smaller aperture in proportion, and the whorls 

 more rounded at the sides. This species includes L. 

 pattila, L. tenelrosa, and L. saxatilis. 



L. littoralis, perhaps more frequently met with than the 

 other sorts, is one with a yellow or yellowish-brown, 

 smooth, oval shell, which has a flattish spire, and a 



