S T R /E A. 



Fig. r.5. h, Mus. Taylor. 



A beautiful group of young .sp(.'cimcn.s of Ostnm 

 Alyiinnsis, .'^owerby, growing on :i mangrove root. 



Species 77. (Fig. a. h, Mus. 15an-lay.) 



OsTP..E.\ Barclaya.va. Cm. Ifintd siiUxli'i. urcuald, reni- 

 formi, lonf/itudiitaliter prodactd, ininquilalerali, 

 valvA superiori palliile fnlvA, ml maryinein ven- 

 tralem postire aciiminatd, prop'e et ad marginem 

 costetlU parvis divaricallm duplicalis sndplA ; 

 valvd in/erioii. prope vianjinem ptirpured, ad 

 marginem albd, plicatd, Jenlaid, uUrd valvam 

 superiorem longe productd ; cicatrice utraque valvd 

 reniformi, caslanea : postic? mblateraU, marglne 

 interna valvm supcrioris dcuiiculato. inferiuris in- 

 dentato. 



Barclay's Ostu.ea. SIigII solid, arched, reniforni, 

 longitudinally produced, inequilateral, U[)pcr valve 

 pale brownish, acuminated posteriorly at the ven- 

 tral margin, near to and at the margin sculptured 

 with little divergently duplicated riblets ; lower 

 valve near the margin jjurple, at the margin 

 white, pHcated, toothed, produced far beyond the 

 upper valve; cicatrix in e.-ich valve ronilbrm, 



of upi>cr valve dentirulate.l, .,f the under in- 

 dented. 



SowEltisY. 



Hah. Point de Fhui, Mauritius. 



iJy specimen 

 attached to a 



eautilul 

 1. The 



Species 78. (Fig. a. h, Mus. Ilanley.) 



CsTli.EA i'KS-Tii-,ins. Ost. tr^ld ti'unj, compressd, longi- 

 tadlndlltrr <,/if,i,iij.l. an-iuihi, sii/i<'nir siih:ilt''iiiintd, 

 vershii nmnjinrm vndralrm nhli,,nr c.,-/nni.s,i. j>a/- 

 lidejulfd, jiiir/Jiin',i rndiKtiiib nl dwariailiiti stri- 

 gatd ct liii'iili'i , viilrd inforiorl divaricatini 

 plicald, alhi-iiia iihu/iiiliuliiie sii.pcranli, plici.< 

 tubercidis nigri.)-/iiir/iiirri.s uniiatis, (id h'riniiKis 

 marginales prodm-fis, iiiigi//,i/ls : lutlcis inlus 

 all/is ; cardiiie pnrro. 



Thi: lAi's-Kdor (),sTi:,EA. Shi-U thin, compressed, 

 longitudinally oblong, arched, attenuated above, 

 oldiquely expanded towards the ventral margin, 

 jiale brown, divergently radlately striped and 

 lineated, lower valve divergently plicated, ex- 

 ceeding the other in size ; plica3 armed with 

 blackish jiurple tubercles which are produced and 

 talon-like at the ends; valves white within; hinge 

 snuill. 



Hanlky. Proc. Zool. Soc. l.Sl.'j. 



Hab. .' 



wliich our tigure is taken does 

 slightest allinity with 0. folium 

 vnbed. 



■;i>ecies 70. (.Mus. Hanley.) 

 i^A. i)st. /('sId compresxd, teniii, versus 

 (iriiiiiiiialii, (iijrk sub-otundd, rugatd , 

 ,,.;■„.,■, si,;„i, hd,if,rniis nigro-pnypurei^ 



oysti 



sculpture consisting of divirgent riblets near the 

 outer margin of the ujipcr valve, which may have 

 been characteristic of the whole surface if it liad been 

 preserved, is sufficient to distinguish the species, lie- 

 sides its semilunar form and the beautifully fluted and 

 toothed raised margin. I linvc ]ileasure in dedi- 

 cating this species to Sir L):Lvid lianlay, Bart., to 

 whom I am indebted for much valuable inlbrmation, 

 and whose indefatigable researches in the Mauritius 

 and its neighbouring i-slets. have led to the accumula- 

 tion of a magnificent collection. 



Nov 



upjper valve armi'il with tube-sluqied blackish- 

 purple outstanding spines. 

 QuoY. Voy. Astrolabe, v. ;!, j.l. 7(i, f l-'l, 14. 



This may possibly be a young speciiuen of Oslrwa 

 cucullata, or gJoinerntti : but it has none of tlie usu;il 

 characteristics of either of those species when tiilly 

 develoiied. The only indication of a connexion is 

 the fact that a few spines are occasionally developed on 

 some very young specimens of 0. cucullata. See 

 ]ilate xxii. f .jl', h. 



r. 1S71. 



