MACTRA. 
73 
and pointed; the three anterior ones broader and shorter ; 
the base flat, concentrically wrinkled, seated in a kind of 
obconic hollow cup much resembling.the Patella Mitrula 
reversed, to which the shell is connected-by a ligament, 
but with which it has no internal communication : lid of 
four valves ; the front pair rough with decussate stride; the 
hinder pair longer, and a little hook ed forwards : color livid 
brown, purplish towards the pointed ends : length half an 
inch; diameter rather less. 
Devon and Dorset coasts, so imbedded in a blackish re¬ 
ticulate kind of sponge, that only the points of the valves 
are exposed, and in which they may be detected, by run- 
sing the Angers over the sponge and feeling the prickly 
points : rare. v. v. 
20- Lepas Verruca. Wart-shaped Acorn-shell. 
Lcpas Verruca. Wood , pL .9. f. 5— Walker,1. 87- 
Lepas inteitexta. Pennant , pi. 4 1 , lower figures. 
Balanus intertextus. Donovan, pi. 36. f. 1— Dorset Cat. 
pllf.9. 
Shell white or brown, flat or compressed, with four 
valves; two of them larger, interlacing until each other 
like the fingers of the hands when pectinated, and strongly 
r.bbed in a direction obliquely to each other ; two of them 
very minute : aperture oblique, closed by the lid, which lias 
t vo very obscure valves ; the base irregularly serrate at the 
margin: length at the base hardly a quarter of an inch. 
On shells and stones, and in the roots of Fuci. v. v. 
21. Lepas radiata. Radiated Acorn-shell. 
Wood, pi. 7- f. 7- 
Shell thick, smooth, marked with longitudinal violet 
rays: valves six, triangular, with the rays.close together at 
the points, but more open at' the “base; the intermediate 
spaces highly polished, and very finely striate transversely: 
length a quarter of an inch ; breadth at the base five eighths. 
Found by Mr. Sowerby fixed to the’ bottom of a ship. 
MACTRA. 
Shell with two equal valves, unequal at the 
sides; hinge with the middle tooth complicated or 
