50 Mr Logan on the Habits of Testaceous MuUusca. 



and complete. On the contrary, of those that were feeding 

 and active, some had nearly completed, others little more than 

 commenced, their intended new addition ; in fact, they were 

 found in many shades of advancement in regard to the new 

 augmentations to their house, the lip of the new piece being 

 in general so soft tliat it yielded to the slightest touch of the 

 finger. On removing the calcareous crust from those dor- 

 mant and operculated, they shewed little or no signs of life, 

 except when excited by pricking or otherwise, when they 

 would slowly withdraw themselves back into the shell. On 

 leaving them to repose, they very slowly returned to the for- 

 mer position. Such as were active and feeding, shewed great 

 excitability ; the slightest touch made them rush into their 

 shell with a gurgling noise : but, when left to themselves, they 

 soon returned and shewed their tentacula, which the others 

 never did. 



Lamarck has occasioned some doubt respecting the branchial 

 organization of the animals in this genus, by conjecturing that 

 they may breathe either water or air : surely he does not mean 

 the one and the other alternately. That many of the species 

 of this genus feed upon the banks of rivers and stagnant wa- 

 ter is very true, but there exists no proof of their ever breath- 

 ing water, since we find many belonging to other genera 

 whose principal, and some whose constant, abode is in that 

 element, breathmg nothing but air. If he had taken the 

 trouble to examine for himself, no room for conjecture would 

 have been left, as the animal in question is only provided with 

 low reticulated branchial cordonets, not standing up in tufts, 

 filets, plates, pectens, or vascular knobs, — evidently exposing 

 too small a vasculai- surface for the action of Avater on the 

 fluids. Besides, none of the animals of this genus that I have 

 ever seen are provided with an operculum ; a fact that La- 

 marck very justlj- sets out with at the commencement of his 

 arrangement of land and fresh-water shells, as being a certain 

 proof that they only breathe free air. As to the localities 

 where the moUusca in question are found feeding and dor- 

 mant, we may mention that they ai'e a cluster of small islands, 

 in general very precipitous and craggy, with rocky and steep 

 shores, or huge blocks of stones piled upon one another. The 



