MACTRA. 73 



and pointed ; the three anterior ones broader and shorter ; 

 the base fiat, concentrically wrinkled, seated in a kind of 

 obconic hollo w 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 striae; the 

 hinder pair longer, and a little hooked 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- 

 ning the fingers over the sponge and feeling the prickly 

 points : rare. v. u. 



20. Lepas Verruca. Wart-shaped Acorn-shell. 

 Lepas Verruca. Wood, pi. 9. f. t> Walker, f. 87- 

 Lepas intertexta. Pennant, pi. 4 1 , lower figures. 

 Balanus intertextus. Donovan, pi. 36. f. 1 Dorset Cat. 



pi. l.f.9. 



Shell white or brown, flat or compressed, with four 

 valves ; two of them larger, interlacing with each other 

 like the fingers of the hands when pectinated, and strongly 

 ribbed in a direction obliquely to each other ; two of them 

 very minute : aperture oblique, closed by the lid, which has 

 two 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 : 

 Ungth 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 

 $ides : hinge with the middle tooth complicated or 



angular^ 



