256 AVICULACE^. 



406. — Brit. Marine Conch, p. 111. — Brown, Illust. Conch. 

 G. B. p. 75, pi. 26, f. 3. 

 Pinna muricata, Da Costa (not of authors) British Conchol. p. 240, pi. 16, f. 3. — 

 Donov. Brit. Shells, vol. i. pi. 10. — Crouch, Introd. Lam. 

 Conch.pl. 11, f. 4. 



„ imjcns, Mont. Test. Brit. p. 180, 583, and Suppl. p. 72. — Maton and 

 Rack, Trans. Linn. Soc. vol. viii. p. 113. — Turt. Conch. Dic- 

 tion, p. 148; Dithyra Brit. p. 222, pi. 20, f. 1.— Fleming. 

 Encyclop. Edin. vol. vii. pi. 206, f. 3 ; Brit. Anim. p. 406.— 

 Couch, Cornish Fauna, pt. 2, p. 34. — Macgilliv. Moll. Aberd. 

 p. 240. — Brit. Marine Conch, p. HI. — Brown, Illust. Conch. 



G. B. p. 75, pi. 26, f. 1 Dillw. Recent Shells, vol. i. p. 325. 



— Lam. Anim. s. Vert. (ed. Desh.) vol. vii. p. 66. — Index 

 Testaceolog. pi. 12, Pinna, f. 3. — Hanl. Recent Shells, vol. i. 

 p. 253, pi. 12, f. 3. 



„ leer is, Donov. Brit Shells, vol. v. pi. 152. 



„ papyracea, Turt. Dithyra Brit. p. 224, pi. 20, f. 3. — Fleming, Brit., 

 Anim. p. 407. — Brit. Marine Conch, p. 112, 



„ rohindata, Couch, Cornish Fauna, pt. 2, p. 36. 



„ eleyans, Brown, Illust. Conch. G. B. p. 76, pi. 26, f. 2. 



The members of this genus, which, from the usual 

 abrasion of their spinous sculpture with advancing age, are 

 far more characteristic in their earlier state, become occa- 

 sionally so altered in outline, when old, that several spe- 

 cies have been constituted (as in the present shell, in the 

 nobilis of the Mediterranean, &c.) from the different stages 

 of increase. 



The valves, which are of a lighter or darker horn-colour, 

 and neither rayed nor mottled with any other hue, except 

 that near the umbones they are shaded with somewhat 

 metallic tints of dirty green or smoky purple, are semi- 

 transparent when young, moderately ventricose, and strongly 

 hiant at the broader extremity. About a dozen slightly 

 elevated rounded narrow ribs emanate from the beaks and 

 radiate posteriorwards, but often in the young, and almost 

 invariably in the adult, become obsolete before they reach 

 the hinder extremity. These, however, do not occupy the 

 entire surface of the shell, since the lower or ventral portion 



