MOLLUSC A TUNIC ATA. 
149 
The author ascribes the perforation of this animal into stone to a 
solvent acid, and supposes that it must be developed in very small 
quantities at the same time, otherwise the shell itself would be attacked 
by it. He supposes also, that the animal has it in its power to apply the 
acid to any place where it wishes to work ; and that it can lessen its 
etfects by diluting it with water, if the acid should endanger the shell. 
He supposes the small tubular openings, w'hich Rang thought were for 
the passage of a byssus (which, however, is not to be found), are for 
filling up the cavities often left by other animals, in perforating the 
stone, and so closing up all entrance to its abode. They may be, how- 
ever, quite accidental, and not special characteristics. These animals 
undergo great alteration at different periods of life, by which one may 
be misled to distinguish them into different species. The author reduces 
them to four, which he has figured on three plates, viz,, — C. aperta, 
Sow. (O. lata, Brod. and Desh. ; C. sicula, delle Chiaje) ; 0 . halanorun, 
Scacchi ; C. elongata, Brod., and C. melitmsis, Brod, 
TUNIC AT A. 
There are some new species of this division, in Moller’s work 
already quoted : viz. — 
Cynthia glutinans ; yellow, thin, covered with sand. 
Ascidia monoceros ; cylindrical, tuberculated, pale red, with a horny 
projection between the openings. A. lurida ; flat, brown-grey, smooth; 
openings lateral, blackish. 
Clavelina cristallina ; spherical, pedicled, compressed above, clear 
like glass, minutely tuberculated, openings whitish. 
Boltenia ciliata ; kidney-shaped, brown-yellow, tuberculated, fringed 
with hairs ; openings reddish ; pedicle granulated, fringed at the end. 
19f> 
N 
