298 TESTACEOUS MOLLUSCA. 



subtruncated at the apex, violet-brown ; the lamella? so arranged as 

 to form indistinct radiating sulci. If. Timor. The iimbones are 

 stated to be smooth and white ; but the solitary type [evidently imma- 

 ture) is too rubbed for this to be regarded as a characteristic. 



O. Tulipa. Lam. 10. Oval-oblong, rather thin, tortuous, violet ; 

 upper valve not flat, with somewhat scabrous longitudinal sulci: 

 lower valve rayed with white and red : inside white. 2. Hab ? 

 " Probably a variety of Mytiloides " (Desh.). The type reminds me 

 of certain specimens of Rhizophor^e. 1 



O. Scabra. Lam. 12. Oblong, spatulate, thin, subpellugid, 

 whitish, armed with longitudinal prickly striae. 2. America. The 

 type in the French Museum is referred to the genus Placuanomia of 

 Broderip. I unfortunately neglected to examine the specimen. 



O. Rostralis. Lam. 13. Oblong, thin, imbricated by loose 

 lamellae, tawny-grey tinged with violet, sharp at the beaks, which are 

 white, small, subequal, approximate, inclined to the left; posterior 

 depression gaping. If. America. Valves of nearly equal length. 



O. Parasitica (in part). Gmel. 3336. — Lam. (in part) 14. — Desh. 

 in E. 2, p 295.— 0. Arborea, Ch. f. 881?— D. p. 279.— W. t. 11, 

 /. 71 ? — O. Rhizophor-E, Guilding, Z. J. 3, p. 542. — Conch. Mis. O. 

 1. 1,/. 1, 4. Ranging from ovate to elongated oblong, thin, glabrous, 

 parasitical, generally broader and more or less rounded at the base ; 

 upper valve more or less depressed, covered (when perfect) with thinly- 

 spread, very flat and not at all curly imbricated flakes, which are either 

 variegated with radiating purplish brown lines or markings on a ground 

 of yellowish white, or are chocolate-brown with a few whitish or yel- 

 lowish rays : lower valve deeper and more ample, rayed with white 

 and brownish or reddish purple, armed with a few distant radiating 

 ribs that are adorned here and there with more or less obsolete elevated 

 scales, often with a few loose concentric lamellae : inside whitish, 

 showing the external colouring towards the edges, which are neither 

 laciniated nor denticulated : cartilage green, its cavity shallow. Up 

 to 4. W. Indies, on the roots of the mangrove. Some individuals 

 with a linguiform shape and a truncated base answer the description of 

 0. Lingua. The Honduras variety, of an uniform dirty purple, and 

 with the ribs almost, if not wholly, obsolete, may prove identical with 

 0. Tulipa. 



1 0. Brasiliana. Lam. 11. Thin, oval, dilated above, small, 

 somewhat rayed with white on a fulvous ground : upper valve slightly 

 convex : transverse striae very fine. Brazil. The type (a small flat 

 shell J, surmised by Desha yes to be a variety of Borealis, is too young 

 to exhibit the permanent characteristics. 



