346 LITTORINID^E. 



organs are nearly those of L. littorea. The sexes are distinct 

 in all the Pectinibranchiata *. I ought to have mentioned 

 the suboval corneous dark operculum, pointed superiorly with 

 about two rapidly increasing gyrations, the nucleus being at 

 the basal end. 



This species is one of those that inhabit the highest levels 

 of the littoral zone, and often dwells for an indefinite time far 

 beyond even the spray of the sea. It appears a mystery how 

 the branchiae are kept moist : I suspect the minute saline 

 particles carried by the winds suffice, especially as the long 

 exposure to atmospheric influences has almost rendered the 

 branchiae of pulmoniferous quality. They clothe the rocks in 

 myriads on the South Devon coasts. I sum up, and conclude 

 the present species to be a true Littorina. 



I mentioned above, that I was preparing further observa- 

 tions on that branch of the Littorinidan family which is termed 

 Lacuna, and that I had reserved the description of the Litto- 

 rina littoralis as a standard of comparison with its animals : 

 I also stated my opinion, that they ought to merge in Litto- 

 rina as species. I now present notes thereon, which I beg 

 may be considered the sequence and termination of my former 

 observations, and which, with the addenda, will render them 

 nearly complete. These notes are the result of an examina- 

 tion and comparison of many living examples of the Littorina 

 littoralis and the Lacuna pallidula of authors, which latter 

 species, with me, will now be the type of a section of the Lit- 

 torina, as I am confirmed in my views that the genus Lacuna 

 is superfluous, and its species ought to pass to Littorina. 

 My remarks embrace the Littorina vincta, "puteolus" and 

 " crassior," which, with the L. pallidula, include all the varie- 

 ties of the Lacuna of authors. I am inclined to think I have 

 named more species than really exist, and that they may be 

 reduced to three, the " crassior " being considered, when de- 

 nuded of the epidermal laminae, a strong, elongated, smooth, 



* Since this was written I have found reason to doubt this conclusion, 

 as will appear hereafter. 



