86 MUREX. ROCK-SHELL . 
by the curvature and groove along the upper and anterior 
margin ; by the diagonal depressed line from the hinge to 
the anterior front margin ; by its coarse and thick texture; 
and by the teeth. 
Da Costas figure, from which that in the Dorset Cata- 
logue is copied and most descriptions drawn, is a very in- 
correct one; and his text and all his references apply only 
to M. Lutraria. Mr. Dillwyn, in his careless manner, gives 
the length as about two inches, and the breadth rather 
more than half as much. 
At the mouths of rivers : very rare. v. m. 
MUREX. ROCK-SHELL . 
Shell with a single valve, spiral, often rough 
with membranaceous folds or protuberances: aper¬ 
ture oval, ending in a straight entire canal, which 
is sometimes a little reflected. 
\v „ - 
1. Murex Carica. Date Rock-shell, Fig. 26. 
Lister , pi. 880. f. 3. b. 
Shell pyramidal, coarse, thick, dull reddish-grey with a 
few chocolate-brown longitudinal marks near the inner-lip, 
irregularly striate and somewhat scaly lengthways; about 
the canal are a few transverse striae, on which there is a 
broad raised rounded protuberance running a little ob¬ 
liquely : spires six, hardly raised, with a row of seven or 
eight pointed protuberances round the top of the two first 
volutions, which on the body-one are concave and triangu¬ 
lar, and about half an inch long; these, however, become 
gradually closed and smaller, decreasing at length into 
raised tubercles which become indistinct towards the 
point; the lesser volutions are finely striate circularly; 
aperture triangular, large, extending to four-fifths of the 
shell, and reaching to the second row of protuberances: 
inside white, polished; the outer-lip broad and thin, with a 
few faint strias near the smaller end, which give the mar¬ 
gin a slightly toothed appearance ; near the larger end the 
margin protrudes into an angular hollow, in consequence 
of its junction with one of the concave protuberances; pil- 
