418 I'HOLADACEJE ; GASTROCH2ENA, CLAVAGELLA, ASPERGILLUM:. 



parts of the world ; and on the coasts of the Atlantic they are 

 used as food, their flesh being reputed more delicate than that 

 of Oysters. According to Seba, who made his observations in 

 Holland, certain species of Nereis ( 910) are mortal enemies to 

 the Teredines, penetrating into their tubes and devouring them. 

 As a British animal, the Teredo is now nearly or quite extinct ; 

 the precautions taken against it having prevented its multiplica- 

 tion : and new importations being checked by the general use of 

 copper sheathing. 



1046. In the Gastrochcena, the valves bear a still smaller 

 proportion to the shelly tube, which not only covers the part of 

 the excavation posterior to the animal, but lines the whole inte- 

 rior 01 the hollow, so as to include the valves. This tube is often 

 found in the perforations previously made by some other boring 

 Mollusk, and also in natural hollows in rocks, corals, &c. ; but 

 the animal has evidently the power of exca- 

 vating for itself, if it does not meet with a 

 hole adapted to it. The Clavagella is an 

 animal of analogous structure ; but one of its 

 valves is incorporated, as it were, with the 

 shelly tube, the other remaining free. The 

 latter appears to perform by its movements 

 the same kind of function as the pallettes of 

 the Teredo. The Aspergillum departs more 

 widely from the general type, than any of the 

 preceding ; so that, if viewed out of con- 

 nexion with them, its true place in the scale 

 would be doubtful. The shell, which derives 

 its name from its resemblance to the spout of 

 a watering-pot, has the form of an elongated 

 oone, terminating at the large end in a disk, 

 which is pierced with a number of tubular 

 orifices ; and the tubes of the outer row being 

 the longest, they form a sort of corolla 

 la, Fig. 698) around the disk. At a little 

 distance above this, two small valves (Z>), in- 

 corporated in the substance of the tube, are easily distinguished. 

 The smaller end is open, and there is likewise a little fissure 



Fro. 698- ASPBR- 

 OILLUW. 



