60 MARINE FAUNA OF ST. ANDREWS. 



shells and tunnels of the mollusks themselves. The 

 epidermis of the latter in each ease would likewise suffer. 



II. That the holes are made by rasping effected by siliceous 



particles on the foot of the mollusk (Hancock), by grains 

 of silex from the exterior (Bryson), by the foot in 

 some way (Dr. Fischer), by chitine in the cirripedes 

 (Darwin) and gephyreans and the bristles of the annelids. 

 This explanation is not borne out by the case of the 

 sponges, by that of the Bryozoa, and certain cirripedes ; 

 moreover such siliceous particles are rare in boring 

 mollusks. 



III. That the excavations are due to ciliary currents, aided 

 by rasping (Garner). 



The currents may assist, but seem to be insufficient to 

 account for the borings of any group. 



IV. That the perforations arc produced by a chemical solvent : 

 Gray, Osier (for Saxicava) , Drummond,Cailliaud, Mantell, 

 Thorent, Reeve, Bouchard-Chantereaux, Spence Bate, 

 Darwin (for Verruca), E. R. Lankester, and Parfitt. 



This will not explain the borings in wood, aluminous 

 shale, gneiss, granite, sandstone, and wax. It is interest- 

 ing, however, as my friend Mr. Ray Lankester has spe- 

 cially shown, that shells and calcareous rocks are much 

 affected by burrowing marine animals. 



V. That the borings are the result of a secreted solvent and 



rasping action (Thompson and Necker). 



1 1 seems improbable that the solvent should vary with 

 the nature of the rocks attacked. 



VI. That the perforations are caused by a macerating or simple 

 solvenl action of the foot in mollusks (Sellius, Deshayes, 

 and (<\v\ 11 Jeffreys). 



It is doubtful if this would be supported by the action 

 of the sponges, Bryozoa, annelids, gephyreans, and cirri- 

 pedes. The stria 1 in certain *<i' the tunnels of the shell- 

 fish are also somewhat at variance with this notion. 



The most interesting species in regard to rarity are Lima 

 subauriculata and L. Loscombii, which come from deep water, 

 the characteristic Lima hians of our southern and western 



