ANATOMY OF THE LAMELLIBRANCHIATA. 301 



tion of the ciliated foot and tentacles causing a never-ceasing 

 vortex at the inferior extremity of the cell. In some of these 

 animals, too, the body is much produced, having the tube of 

 its mantle garnished with its continuous branchiae, the cilia 

 of which must give great force to the rushing column of wa- 

 ter. If any species make use of its valves as adjutory, it 

 would be the Teredo, which attacks the hard planks of ships. 

 On inspection, these certainly seem well adapted to act as 

 line rasps j and though it has been said by Turton that they 

 do not correspond with the bore, they perhaps are so used, 

 aided however by the action of the water: here however, par- 

 ticularly in the young animal, they are very fragile, and would 

 break if used in a violent rotatory manner. It may be added 

 that the author has found the Pholas conoides in timber, al- 

 though its valves do not seem in the least adapted for such 

 an action. According to Home, 1 Hatchett found sawdust in 

 the stomach of the Teredo, but it is questionable whether this 

 was anything more than the ordinary pulp therein contained. 



Certain Annelides apparently possess this power of exca- 

 vation. The rocks on our coast are pierced by a minute 

 worm, probably of the genus Diplotis of Montague. Its mouth 

 does not seem adapted for such an action, and many, like the 

 one just named, have their branchiae, mouth, and tentacular 

 appendages ciliated ; but it remains for future investigation 

 to decide whether this circumstance gives them the power 

 which they possess. It appears to be from the action of Vor- 

 ticellae and other vibratile animalcules, that the erosion noti- 

 ced in so many shells at the beaks, particularly the fluviatile 

 ones, takes place. At the beaks the laminae are softer, and 

 more distant from each other, so that they are more easily 

 acted upon by destructive agents. We find the valves of the 

 oyster, Pecten, Lutraria, &c. perforated by small circular 

 apertures externally, leading into internal cavities. Dr. Buck- 

 land 2 showed this to depend upon the action of a zoophyte, 

 which Professor Grant 3 has particularly examined, and named 

 Clionia celata. Dr. Buckland considers the holes to be form- 

 ed by little borers, which the polypes possess : these, how- 

 ever do not exist, and the author believes the phenomenon to 

 be caused by the action of the cilia of the animal. 4 



All the Lamellibranchiata are inhabitants of the water, al- 

 though some will live for months in a dry place, provided the 



1 Lectures on Comparative Anatomy. 

 2 Rev. W. Coneybeare, on a remarkable class of organic impressions, Geol. 

 Trans. 1814. 3 Fleming, British Zoology. 



4 Many otlier animals, as some of the Cirrhopoda, Radiata, &c. excavate 

 the rocks without any apparent mechanical means. 



