THE COMMON MARINE SHELLS OF THE BOMBAY SHORE, 214 
but apparently they are not above attacking the bivalves when they 
come across their path. Now Semele cordiformis, as far as my obser- 
vations go, is not one of the bivalves that burrow deeply into the sand, 
and if, as I suspect, the shell was barely immersed, the univalve on 
touching it whilst gliding along would easily prevent any further 
burrowing. | 
Any one who has attempted to remove or push aside the common 
limpet knows what adhesive or suctional power the animal has in his 
foot, and it must be this power that renders the bivalve helpless when 
once caught. Jam unfortunately unable to give any account of the 
actual process of the boring, as Urosalpins sat on the top of his prey and 
performed all his offensive actions under cover of his shell ; but the 
Semele was bored as stated and devoured, and those little scavengers— 
the hermit crabs, of which I had several in my tank—soon scented what 
was up and assisted at the feast. 
Conchological books inform us that certain members of the snail 
tribe are provided, like spiders, with a viscous thread, by which they can 
let themselves down from the branches of trees, and it appears that some 
marine shells can draw themselves up by a similar means. I was fortu- 
nate enough to find a live specimen of, I believe, Scalaria consors, to which 
was attached by a thread a small sort of anchor consisting of several 
bits of shell agglutinated together. The shell is extremely light, and it 
seems reasonable to suppose that the animal having secured its 
anchorage would, or at any rate could, float in mid-ocean, and the shell 
being a dull white would not be readily seen in such a position. 
As Mr. Phipson is reprinting, with the accompanying illustration, the 
descriptions by Mr. Melvill of twenty-five new species found here, I 
have not considered it necessary to refer to any of them in this article, 
THE UNIVALVES OR GASTEROPODA. 
The order I follow is that given in the article on the Mollusca in the 
Encyclopeedia Britannica. 
Diviston I..—Shield shape or conical hollow shells with an oval base. 
Divisrton II,.—Shells, the mouth of which is generally circular or 
semi-circular and noé produced into a canal at the base. 
Diviston I1I.—Shells, the mouth of which is produced into a canal 
at the base. The mouth is sometimes a sort of canal in itself. When 
