52 LITTORINIDiE. 



acute, much arcuated. Pillar-lip not suddenly broad ; 

 its outer edge very concave. Length four lines and a 

 half; breadth five lines. 



The more convex whorls, the rounded body, and the 

 absence of any broad basal confluence of the two lips, 

 distinguish it from litt oralis. Mr. Sowerby assures us 

 that similar specimens, whose identity with 'palliata was 

 unquestionable, have been taken on the south coast of 

 England. 



In the preceding account of the British Littorina., several 

 are described as species which many of our ablest natural- 

 ists regard as varieties, whilst others are considered varieties 

 which some hold to be worthy of specific rank. Our own 

 belief is that even the list we have given assigns too high a 

 rank to several forms ; but in order that this difficult sub- 

 ject should be so treated as to enable those who may have 

 opportunity, to work it out still more completely, we have 

 described provisionally as species the leading types or most 

 striking forms, even at the risk of laying too much stress 

 on transient characters. 



Our conviction is that the result of a completed know- 

 ledge of this genus would be a reduction in the number of 

 true British species. Taking the most permanent features 

 of the animal and its shell as our guide, we are inclined to 

 reduce the true specific types to four. 



1. LrrroRiNA neritoides ; a form which is so distinct in 

 animal and shell that it has not been subdivided like its 

 neighbours, nor confounded with them. 



2. LiTTOBiNA LiTTOREA ; tlic characters of the animal are 

 constantU' different from those of rudis ; the shell rarely 



