i> 



Go 



and have fomewhat the appearance of two holes broken 

 into one, which is adapted to the (hape of the tubes of 

 the animaL 



' The inhabitant is an Afcidia, with two very long, flen- 

 der, white tubes, exceeding the length of the fhell ; 

 thefe are connefted togi-ether their whole lengrth, but ter- 

 minated by two orifices, ciliated with flefliy fibres, of a 

 dark purplifli-brown : the body is alfo white; near the 

 pofterior end is ?i foramen, through which, a fmall foot, 

 ox fuflentacidum, is fometimes protruded, and doubtlefs 

 the apparatus, which alTifls in perforating rocks, being 

 always placed in its cell with that end downwards, and 

 incapable of turning. 



It is probable this, as well as all other fimilar animals, 

 whofe habits are to perforate flone, are provided with 

 an acid, or fome folvent menftruum capable of perform- 

 ing that office: it mull alfo be recollected, that this, 

 feemingly laborious talk, is not afPefted in any given 

 time, but is the work of years ; as the chamber for the 

 lodgment of the animal, only requires enlarging as 

 the fliell grows. 



Stone of a vitrifiable nature, is impenetrable to thefe 

 animals, but all fuch as are wholly, or even partly cal- 

 careous, are more or lefs attacked ;* and while this, the 



MyLilus 



* This remark might be attended with confidcrablc national advantage, if 

 purfued with experimental application, under the dircdion and encouragement 



