THE COMMON MARINE SHELLS OF THE BOMBAY SHORE. 216 
Rotella vestiaria (Lam.).—Is the little highly coloured shining shell, 
so common on the sandy beach. It is often pink. The spire is depres- 
sed, and in size it is smaller than a two-anna piece. 
NERITIDA. 
Smallish, thick, semi-oval shells ; mouth large, flat, and in shape 
like a capital D ; columella or central pillar of shell broad, flat, and 
sloping inwards. 
Nerita oryzarum (Recluz).—Very common on half-tide rocks or under 
stones ; colour white and black mottled and streaked, sometimes with 
a tinge of rust; last whorl envelops nearly the whole shell and is 
ridged ; shell polished. 
Neritina crepiduiaria (Lam.).—Apex bent down towards mouth of 
shell; colour white, with purple transverse bandings ; shell quite 
smooth ; frequents muddy places on the harbour side of the shore. 
IANTHINIDA, 
Lanthina communis (Lam.).—Is a very fragile and beautiful shell, 
The upper half of the whorls a delicate white purple; the under or 
aperture side a deep purple. It is a floating shell, and only found 
when washed up after stormy weather. It also, I am told, has been 
procured in a very perfect state from fishermen’s nets. 
CERITHIIDA. 
Cerithium morus (Lam.) and Potamides (Tympanotonos) fluviatilis 
(P. M.).—These two little shells live along with Planawis at three- 
quarter tide mark, especially where there are muddy stones. The latter 
seems to belie its name, at any rate as far as Bombay is concerned. 
C. morus is a blackish, small and spiral shell, with sometimes a white 
band ; spirally striated and heavily beaded, and regularity of shape 
interrupted by varices or thickened ridges ; mouth—outer lip rounded 
and thickened, causing the varix as the growth of the shell is continued 
leaving the thickened part standing out; about }” to #" long, 
P, fluviatilis is a slender pyramidal shell, about 3" to 1” long. Each 
whorl has three rows of spiral beadings ; mouth produced and flattish 
at the base ; last whorl often shows marked white and black spiral 
bandings and is smooth. 
TURRITELLIDA. 
Turritella duplicata (am.) is a massive tapering shell, having ten 
to fifteen or more whorls; easily known by two parallel ridges 
