Mr. W. Clark on the Lacuna. 29 



IV. — Observations on the Lacunae. By William Clakk, Esq. 

 To the Editors of the Annals of Natural History. 

 Gentlemen, Norfolk Crescent, Bath, May 1850. 



I MENTIONED in my paper on the Littorinida in the May ' An- 

 nals/ 1850, that I was preparing a memoir ob that branch of 

 the family which is termed Lacuna, and that I had reserved the 

 description of the Littorina littoralis as a standard of comparison 

 with its animals : 1 also stated my opinion, that they ought to 

 merge in Littorina as species. I now present notes thereon, 

 which I beg may be considered the sequence and termination of 

 my former paper, and which, with the addenda, will render it 

 nearly complete. The present observations are the result of an 

 examination and comparison of many living examples of the Lit- 

 torina littoralis and the Lacuna pallidula of authors, which latter 

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

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

 superfluous, and its species ought to pass to Littorina. My re- 

 marks embrace the Littorina vincta, " puteolus " and " crassior," 

 which, with the L. pallidula, include all the varieties of the Lacuna 

 of authors. 1 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 denuded of the epidermal 

 laminse, a strong, elongated, smooth, plain light brown subcari- 

 nated variety of that variety termed " quadrifasciata," which I 

 have seen with the same oblique epidermal laminse ; but as the 

 animal of the " crassior " has not been observed, this view cannot 

 be received as certain. Though I have only examined the L. 

 pallidula, I have little doubt that in all essentials the other spe- 

 cies called Lacuna agree with this type of a section of the Lit- 

 torina, making allowance for the variation of species. I have 

 given copious notes of the L. littoralis in comparison with the 

 Littorina pallidula, mihi, and leave it to malacologists to draw 

 their own conclusions, reserving to myself, as a finale, a short 

 comparative summary. 



Littorina littoralis, Linnseus. 

 Animal spiral ; mantle pale yellow, fleshy, but even with the 

 margin of the aperture ; the head is a cylindrical wrinkled muzzle 

 capable of considerable extension, usually pale red on the neck, 

 but the colours are very variable in this species, being yellow, 

 orange, red-brown, and occasionally all the hues of lead-colour 

 to nearly black ; the under part of the foot is always white or 

 yellow-white ; the buccal disk is pale yellow, subcircular, with a 



