66 MOLLUSCA. GASTEROPODA. 



P. Peronii, Cuv. About an inch and a-half long. Inhabits Indian 

 seas Lam. vi. 1, 339. 



P. plumiila, Fleming. (Bulla, Mont.) Cloak broad, reticulated ; 

 foot pointed, pale yellow; shell oval, depressed, pellucid, con- 

 centrically wrinkled, with a minute whorl near one end. 1 inch 

 long. Coast of Devonshire. B. Mont. Test. pi. 15, fig. 9. 



FAMILY VI. PHYLLIDIACEA. 



Branchiae placed under the margin of the mantle, and disposed 

 in a longitudinal series around the body ; respiring in water. 

 Gen. 20. PATELLA, Lam. Lin. 



Body entirely covered by the shell, with two pointed tentacula 

 on the head, and eyes at their exterior base ; branchiae dis- 

 posed round the body under the margin of the mantle ; anus 

 and orifice for generation on the right anterior side ; shell 

 univalve, not spiral, concave, simple and entire, with the 

 summit inclined anteriorly. 



The species of this genus are extremely numerous. The animal possesses little 

 power of locomotion, and generally remains fixed in one spot by its power of suc- 

 tion. Some species were used for the table in ancient times ; and the common 

 species of the British coasts is still gathered by the poorer people for the same pur- 

 pose. 



P. granatina, Lam. Shell ovate, depressed, angular, with distant 

 alternately smaller ribs, and transverse undulated rows of dark 

 scales ; colour white, with reddish brown, transverse, zigzag lines. 

 2 to 3 inches long. Indian seas D'Argenv. pi. 2, fig. G. 



P. testudinaria, Lin. Shell ovate, con vex- conical, with decussated 

 striae, the longitudinal ones largest ; inside bluish silvery ; colour 

 of a red brown, on a pale yellow ground. 3 inches long. Inha- 

 bits Indian seas D'Arge?iv. pi. 2, fig. P. 



P. vvlgata, Lin. Shell suboval, with about fourteen obsolete ribs 

 and intermediate striae ; margin subangulated, dilated, and acute. 

 Inhabits coasts of Europe. B. Perm. Brit. Zool. iv. pi. 92, fig. 1. 

 This species differs so much in size, form, and colour, and the conical and depres- 

 sed varieties run so much into each other, that it is impossible to draw any sepa- 

 rating line. The diameter of a full grown shell varies, from an inch to two inches 

 and a-half ; and the depth in some specimens is more than double that of others ol 

 the same diameter. The general colour is brownish cinereous, but young shells arc 

 striped and marked in various ways with red, white, and yellow, displayed througli 

 the thin shell in beautiful variegations. The number of longitudinal ribs is gene 

 rally fourteen, but also varies considerably, and the surface of old shells is sometimes 

 nearly smooth. 



P. pellttcida, Lin. Shell convex, membranaceous, pellucid, obovate, 

 with from three to seven longitudinal dotted azure rays ; summit 

 obsolete and towards the margin. 6 or 8 lines long. B. Brown* 

 Illust. pi. 37, fig. 11. 



Gen. 21. CHITON, Lam. Lin. 



Body oval, oblong, convex, rounded at the extremities, margin 

 ed all around by a coriaceous skin, and covered above by i 



