46 



Hub. — "Ad Insulas Gallapagos et apud Insulam Lord Hood's diet am. 

 Found in pearl oysters, in from three to seven fathoms." — Sowerby. 



2. R. denticulata, Deshayes, sp. 



Gastrochsena denticulata, Deshayes, Zool. Proc. Lond. p. 327, 1854. 

 Rocellaria denticulata, H. and A. Adams, Genera, ii. p. 336, 1856. 



Description. — " R. testa ovato-ventricosa, brevi, solidula, lata, hiantissima, 

 hiatu ovato, lato, inferne attenuato et tertiam partem posticam testse attin- 

 gente ; valvis subtrapezoidalibus transversim striato-lamellosis, in latere 

 antico striis imbricatis, crispato-denticulatis, in latere postico erectis, distan- 

 tioribus ; latere antico satis elongato, recto, in sutura cristato ; umbonibus 

 tumidulis, subumbilicatis ; ligamento angusto, elongato, fulvo." — Deshayes. 



Hab. — Columbia. Coll. Cuming. 



This is a heavy shell, while R. brevis is thin and pellucid. It is also 

 more prominently striated than that species, and differs from it in shape. 



3. R. dubia,* Pennant, sp. 



Mya dubia, Pennant, Brit. Zool. iv. p. 82, t. 44, f. 19, 1777. 

 Donovan, British Shells, iii. t. 108, 1810. 

 Maton and Rackett, Linn. Trans, viii. p. 33, 1807. 

 Wood, Gen. Conch, p. 102, t. 25, f. 2, 3, 1815. 

 " Index Test, edit. 1, p. 11, 1818. 

 " " " edit. 2, t. 2, f. 23, 1828. 



Gerville, Cat. des Coq. de la Manche, p. 10, 1825. 

 Mya Pholadia, Montagu, Test. Brit. i. p. 28 et 559, et supp. p. 20, 1803. 



Fleming, Edinb. Encyc. ii. p. 87. 

 Chama parva, DaCosta, Brit. Conch, p. 234, 1778. 

 Pholas faba, Pultney, Dorsetshire Catalogue, p. 27, 1799. 

 Pholas pusilla, Poli, Test. utr. Sicil. i. p. 50, t. 7, f. 12, 13, 1791. 



Olivi, Adrit. p. 93, 1792. 

 Mytilus ambiguus, Dillwyn, i. p. 304, 1817. 



Balano minimo, Ginanni, Op. post. ii. p. 35, t. 23, f. 164, 1755 — '57. 

 Gastrochsena Pholadia, Turton, Conch. Dithvra Brit. p. 18, t. 2, f. 3. 9, 

 1822. 

 Lukis, Loudon's Mag. Nat. Hist. vi. p. 404, f. 52, 



1833. 

 Brown, Illust. Brit. Conch. 2d ed. p. 116, t. 48, 

 f. 13, 14, 1844. 

 Gastrochsena hians, Fleming, Brit. Anim. p. 458, 1828. 

 Gastrochsena cuneiformis, Philippi, Enum. Moll. Sicil. i. p. 2, 1836. 

 Gastrochsena Polii, Philippi, Enum. Moll. Sicil. ii. p. 3, 1844. 



Requier, Cat. des Coq. de la Corse, p. 13, 1848. 

 Gastrochsena (Chsena) faba, Gray, Figs. Moll. Anim. v. p. 28, t. 339, f. 2, 



3, 4 ; t. 347, f. 6-8, 1857. 

 Gastrochsena modiolina, Lamarck, Anim. Sans Vert. v. p. 447. 1818. 



" (Desh. edit.) Anim. Sans Vert. vi. p. 



49, 1835. 

 Sowerby. Genera, f. 1, 2, 1820— '24. 



" ' Conch. Manual, f. 52, 1842. 

 Crouch, Introd. Lamarck, t. 2, f. 12, a, b, 1827. 

 Bouchard-Chantreaux, Moll. Boulonnais, p. 8, 



1829. 

 Collard de Cherres, Cat. Test. Mar. p. 9, 1830. 

 Hanley, Desc. Cat. p. 10, 1842. 

 Cailliaud, Guerin's Mag. Zool. Moll. p. 2, t. 69, 



70, 71, 1843. 

 Reeve, Conch. Syst. t. 50, f. 1, 2, 1843. 

 Potiez et Michaud, Gallerie des Moll. ii. p. 268, 

 1844, 



