S T R ^ A. 



Species 2. (Fig. a, b, Mus. Maillard.) 



OsTR^A cucuLLiNA. Ost. testd jMrvA, irregulari, multi- 

 formi, gryphoided, tenui, fragili, valde inmqxd- 

 mlvi,pallide ru/d; valvd sitpen'ori plano-cmicavd, 

 tmuissimd, sublamellnsd, valvd infenon profimdA, 

 ad apicein arcmitd ; ared cardinali an(/ustd, 

 acutd. 



TuE HOODED OsTR^A. Shell small, irregular, multiform, 

 gryplioid, thin, fragile, very iiiequivalve, pale 

 reddish ; upper valve plano-concave, very thin, 

 sublamellar, lower valve deep, arched at the apex ; 

 cardinal area narrow, acute. 



Deshayes. Conchyliologie di- I'lslc de la licunion, p. 2, 

 36, pi. xxxii., f. 78. 



Hab. Bourbon. 



This peculiarly formed little oyster has a prima 



facie appearance of being young and unformed, and 



possibly belonging to some larger species. M. jMail- 



lard, its discoverer, however, declares that it never 



attains a larger size. 



Species .3. (Mus. Sowerby.) 



OsTRiEA MTTiLoiDES. Osl. tesld parositlcd, solidd, ob- 

 longd, versus cardtnem attemuitd, ad latera plicaio- 

 crenatd,profu7ide violaced, obscure radiatd, omnino 

 undulatim-squamosA, margine ventrali subquad- 

 rato; valvuld superiori convexA ; ared cardinali 

 acuiiiinatd. 



The inTiLoiD Ostr^a. Shell parasitic, solid, oblong, 

 attenuated towards the hinge, plicato-crenated at 

 the sides, deep violet, obscurely rayed, wavily 



sqiiamose ; ventral margin subquadrate ; upper 

 valve convex ; cardinal area acuminated. 



Lamarck. Animaux sans vertebres. Ostrava, No. 21. 



Ilidi. Australia. 



Species 4. (Mus. Sowerby.) 



OstRjEA parasitica. Ost. testd ovaio-subrotundatd, ad 

 radices Ehi^ophorarum adhcerenti, pallide fulvd, 

 fusco-purpureo radiatim/asciatdetvariegatd; val- 

 vuld inferiori profundiord, irregulariter squamosd, 

 obscure eostatd; valvuld superiori subcomplanatd, 

 versils margines undulato-squamiferd ; marginibus 

 intiis subpurpureis, haud crenulatis. 

 The parasitic Oyster. Shell somewhat rounded 

 ovate, adhering to Mangrove roots, pale fulvous, 

 radiately banded and variegated with bro\vnish 

 purple ; lower valve deeper, irregularly squamosa, 

 obscurely ribbed; upper valve rather flattened, 

 undulately squamose towards the margins; margins 

 rather purple within, not crenulated. 

 Gmelin. LinntEUs, Systema Natiu'se, p. 295. 

 Hab. Eiver Gambia in Africa. 



The figure is taken from a portion of a forked root of 

 Jlangrove, both limbs of which are completely covered 

 with specimens of various sizes and shapes. These agree 

 in all particulars with those of a magnificent specimen in 

 the British Museum, marked as from the above locality, 

 and with the figure cited in Chemnitz. The South 

 African 0. RhizoplwrcB of Guilding, if not identical mth 

 this species, differs from it in the prevailing form of 

 the shells being more elongated, and of thinner sub- 

 stance. 



October, 1870. 



