172 



Part III. — -Eleventh Annual Report 



REPORT ON MOLLUSCA. By Alfred Brown. 



The methods adopted for the purpose of obtaining specimens of the 

 fish frequenting the various lochs visited by the ' Garland,' and of the 

 food of such fish, were not of a kind very favourable to the collecting of 

 mollusca. The trawl was so wide in the mesh that most of the shell-fish 

 escaped; and the mud, which might be expected to yield the smaller 

 species, was generally entirely washed out. 



The dredge, when used, was usually permitted to fill itself at once by 

 one deep bite into the subsoil, and so produced but few mollusca, yielding 

 more commonly a harvest of mud-frequenting annelids ; whilst the 

 tow-net gave us only pteropods of one species in vast numbers, as well as 

 the fry of littoral shell-fish, such as Lacuna and Rissoa. 



Giving due allowance for these defects in the method of collecting, it 

 cannot but remain a subject for surprise that the mollusca should have 

 been taken in such small numbers and of so few species. There is an 

 almost total absence of the predatory gasteropods Fusus, Buccinum, 

 JVatica, &c, and as there is an equally remarkable absence of the pierced 

 valves of Conchifera, which form their principal food, we must conclude 

 that the whelks in question do not exist in any considerable numbers in 

 these waters. 



No opportunity occurred of examining Broad Bay in Lews, which is to 

 be regretted, as that bay is noted for the number and variety of its 

 bivalves, and it would have been interesting to note if the presence of 

 such a store of food had any effect on the numbers of Fusi, Buccina, &c, 

 in that bay. 



The only point worth noticing in relation to this division is the 

 presence in several of the lochs in Lews of deep sea forms in very shallow 

 water ; such species as Nucula nucleus and nitida, Corbula and Leda being 

 taken in 8 or 10 feet of water, in company with the IAttoi'inxlm&^Trochi, 

 which are strictly confined to the laminarian zone — the forms named 

 being characteristic of the coralline and lower zones. 



It is usual to expect in going north that the shells should present a 

 more robust and developed appearance than in more southern waters, but 

 this was not the case on this cruise — the shells, on the contrary, present- 

 ing a rather depauperated appearance, certainly below the average in point 

 of size. 



LIST OF THE MOLLUSCA OBTAINED. 



Loch Hourn. 



Natica Alderi, 

 Trichotropis borealis, 

 Nassa reticulata, 

 Trochus millcgranus, 



3 

 1 

 1 

 3 

 1 

 1 

 2 

 1 



Kellia suborbicularis, 

 Solen ensis, 

 Mytilus modiolus, . 

 Saxicava rugosa, 

 Tcllina donaeina, 

 Venus ovata, . 

 Lucina spinifera, 

 Psammobia tellinclla, 

 Mactra solida var. elliptica, 

 Cardium fasciatum, 

 Pecten tigrinus, 

 Lucinopsis undata, fragments. 

 Thracia papyracea, . 



1 

 1 

 1 

 1 



4 

 4 

 1 

 1 

 12 



, , tumidus, 

 Littorina rudis, 



,, obtusata, . 

 Chiton (species), 



valve 

 valve 



1 



