366 



Found by Mr. Cuming attached to Mytili, at a depth of six 

 fathoms, off Conception, Chili. 



3. Orbicula tenuis (pi. lxxiii. f. 4, 5.) nobis. 



Testa laevi, tenui, apice ad marginem propinquo. 



Shell smooth, thin, apex of the upper valve near the posterior 

 margin ; disk of adhesion obtusely triangular, close to the hinder 

 edge ; perforation linear. 



4. Okbicula Cumingii (pi. lxxiii. f. 6.) Brod. Zool. Proc. 

 1833. p. 124. 



Testa, subconica, suborbiculari, crassiuscula, striis ab apice 

 radiantibus numerosis, hneis incrementi elevatis decussantibus, 

 epidermide pallide fusca. 



Shell nearly orbicular, subcorneal, rather thick, with numerous 

 striae radiating from the subcentral apex, and decussated by the 

 elevated lines of growth ; epidermis of a pale brown colour. 



Found by H. Cuming, at Payta, St. Elena and Panama. 



5. Orbicula strigata (pi. lxxiii. f. 7.) Brod. Zool. Trans, 

 vol. i. pt. 2. pi. xxiii. f. 1. 



Testa crassiuscula, subrotunda, substriata, radiatim castaneo- 

 strigata ; epidermide tenui fusca. 



Shell rather thick, nearly orbicular, slightly striated, radiately 

 streaked with chesnut colour, epidermis thin, pale brown. 



Island of Cana, Guatemala, Malacca, and Corrigedor ; H. Cuming. 



6. Orbicula striata (pi. lxxiii. f. 8.) Sow. Trans, of Linn. 

 Soc. vol. xih. 



Testae valvula superiore striis elevatis plurimis, ex vertice ad 

 marginem decurrentibus. 



Shell rather irregularly orbicular, thickish, apex nearly central ; 

 upper valve with numerous elevated striae from the apex to the 

 margin. 



This is the species which Lamarck has elevated to the rank of 

 a genus (named Discina), from not rightly knowing his own pre- 

 viously established genus Orbicula. 



Locality unknown ; found in ballast used to mend roads near 

 London. 



CEANIA. 



Testa itiaequivalvis, aequilatera, (subirregularis) rotundato-sub- 



