59 



Rounded, rather flattened, smooth or radiately striated ; 

 spreadingat the sides,ears nearly equal,large,butnarrowedatthe 

 base ; ribs 10, rather rounded, slightly raised near the umbones, 

 flattened so as almost to disappear near the margin, the alternate 

 ones much less elevated. The varieties are too numerous to 

 describe particularly. In those which are variegated the 

 markings are broad, angular and defined. Mediterranean. 



42. P. proteus. (pi. xiii. f. 53, 54 and pi. xiv. f. 83 and 

 84.) Solander. according to Dillwyn. Chemnitz. 207. f- 2042. 

 P. discors, ? 



T. sub-trigona, compressa, sub-inaequivalvi, lasvi ; vel 

 obsolete striata: auriculis sub-sequalibus, sub-striatis, valva 

 sinistra altera magis ventricosa, margine alteram superante: 

 costis latis, rotundatis quinque ; valva. dextra costis quatuor, 

 latis, sub-duplicatis ; colore vario. Long. 1. 65.; lat. 0. 55 ; 

 alt. 1. 70; poll. 



In P. sulcatus there are 10 ribs nearly equal in size; in P. 

 glaber 5 are large, and the 5 intermediate ones comparatively 

 small ; in this species which retains the general form, the 

 intermediate 5 are wanting, but there are gradations between 

 each. The varieties in colour are, plain orange ; orange 

 mottled ; plain purple ; purple mottled ; yellow variegated 

 with grey and intermediate rays ; and greyish, with beautiful 

 zebra-like markings of brown. Adriatic. 



43. P. sulcatus. (p. xviii. f. 179. 180. 181.) Bom. 

 Mus. Ctes. pi. 6. f. 3. 



T. rotundata, sub-complanata, radiatim striata ; auriculis sub- 

 eequalibus, latis, acutangulatis ; costis decern sulcatis, rotun- 

 datis, elevatis, aequalibus ; colore lacteo, fusco maculato, vel 

 aurantiaco, vel fusco-nigricante. Long. 1. 30; lat. 0, 50; alt. 

 0. 20. poll. 



Rounded, rather flattened, radiately striated; auricles nearly 

 equal, wide, rather narrow at the base ; the ribs, ten in number, 

 are sulcated, rounded, elevated, equal, equally raised through- 

 out ; the colour is nearly white, spotted with brown ; there is 

 a purple variety, and one of a blackish brown colour. The 

 shell here described is unquestionably the true P. sulcatus of 

 Born, though possibly P. sulcatus of Lamarck may be only 

 one of the numerous varieties of P. glaber, from which this 

 species differs not only in having the ribs equal, but in having 

 them as much elevated at the margin as at the umbones. 



Mediterranean. 



44. P. unicolor. (pi. xii. f. 5. 6.) Lam. Anim. s. Vert, 

 vi. p. 163. 



