Mr. J. Alder on Lottia virginea. 405 



O' 



ler has been since adopted by Mr. Forbes, who published it 

 as such in his e Malacologia Monensis ;' and in the same work 

 he describes another species which he considers new, referring 

 it to a different genus under the name of Lottia pulchella. 



Having been brought forward as a witness to a fact, the 

 conclusion drawn from which I now believe to be erroneous, I 

 think it incumbent upon me to state the result of some further 

 and more accurate observations recently made upon the same 

 species, which is not uncommon on the coast of Northumber- 

 land, where I have had frequent opportunities of collecting it 

 alive of all sizes during the last and preceding summers. 

 When examined attentively with a magnifier of moderate 

 power, a falciform process may be seen issuing from a cavity 

 on the back of the neck, proceeding behind the head and ter- 

 minating in a curve on the right side of it. This process is 

 capable of great extension and contraction, and a free action 

 from side to side of the cavity, at the will of the animal. When 

 withdrawn it is not visible from below, a circumstance which 

 may account for its having been overlooked. It contains two 

 large vessels running on opposite sides through its whole 

 length ; these are again crossed at right angles by smaller 

 ones forming projecting rings. Thus when seen at a side, the 

 edges appear smooth as in fig. 1 ; but when viewed either on 



Fig. 1. Fig. 2. Fig. 3. 

 the back or front, it assumes a strongly pectinated or plumed 

 appearance (fig. 2 and 3). The whole surface is seen to be 

 ciliated under a high magnifier. There cannot be a doubt 

 that this process is the true branchiae of the animal ; in addi- 

 tion to which, however, there is, as remarked by Dr. Johnston, 

 a dense fringe of filaments completely surrounding the cloak, 

 and bearing a strong resemblance both in position and ap- 

 pearance to the branchial fringe of Patella. Its situation how- 

 ever is nearer the margin of the cloak, and instead of being 

 composed of flat leaflets as in that genus, it consists of nearly 

 linear filaments of unequal length with thickened ends. It is 

 banded with pink at intervals corresponding with the mark- 

 ings of the shell. The function of this fringe I have not been 

 able satisfactorily to ascertain. It is possible that the fila- 

 ments may be accessory branchiae, thus forming an interme- - 



diate link between Lottia and Patella, so nearly allied in all 



