OF MOLLUSCA. 171 



transparent. Teeth 2*2, small, transparent ; apex black, opake ; the 

 inner close together, with elongated oblong roots and small rounded 

 apices ; the outer larger, with short broad oblong roots, and a trans- 

 verse three-hooked crown. 



The mantle of a Tectura (like T. testudinalis), from the Sandwich 

 Islands, is thin-edged, narrow, thickened, rounded, with a series of 

 minute rather close tubercles on the margin ; inner surface and sides 

 of the body smooth, without any laminae. Gills elongate, tapering, 

 acute, free the whole length, and prominent. Lingual membrane 

 elongate, rather narrow. Teeth black, conic, curved, in alternate 

 bands of two and four series ; the intermediate ones with only two 

 teeth much the largest. 



The mantle of M. d'Orbigny's specimen of Patella Petrei, which 

 is only a variety of Tectura zebrina, is simple, with a series of rather 

 distant, subcylindrical, fleshy beards, placed in a regular raised line a 

 little within the edge of the under side, continued over the head. 

 Gills small, elongate, simple, tapering to a fine point in front, arising 

 from the hinder part of the left side of the mantle-cavity, and free the 

 greater part of its length, formed of close-set regular transverse laminae, 

 edged on each side by a fleshy band. Vent and aperture of generation 

 each prominent on separate tubercles on the right side of the base 

 of the mantle-cavity. Eyes very small, lateral, exterior. Tentacles 

 subulate. Foot quite simple and smooth on the sides. Rostrum 

 broad ; mouth oblong, transverse ; lips discoid, slightly fringed. 



In the same bottle was a small specimen of the Patella zebrina of 

 D'Orbigny, with exactly the same animal, but it was soft, from 

 the weakness of the spirit, and the submarginal beards were not so 

 distinctly developed. 



The delicate brittle Tectura (Patelloida) depict a, which lives on 

 the surface of Zosteras at San Diego, California, is almost linear, 

 being compressed at the sides, and at least four times as long as wide. 

 — Hinds, Voy. Sulph. 35. 



** Mantle with a series of lamince just within the edge beneath. 



3. Scurria. 



The mantle the size of the shell, simple, on the edge with a series 

 of half-oblong rather distant fleshy laminae just within the edge, con- 

 tinued over the head and behind. Foot oblong, smooth, and without 

 any appendages on the sides. Tentacles subulate. Eyes on the 

 outer side of the swelling at their base. Rostrum short ; mouth 

 oblong, transverse ; lip finely striated. Gill elongate, tapering, on 

 the left side of the gill-cavity over the back of the head ; the end 

 free, floating, formed of very numerous, close, transverse laminae, 

 with a large transparent vessel on the left margin. Tongue-mem- 

 brane linear. Teeth yellow, 3*3? 



Lives in holes in the roots of Fuci, like the Patina ccerulea, D'Orb. 



1. S. mitra, t. 114. f. 1. 



The gill of Scurria mitra is triangular, on the left side of the back. 



