OSTR/EA.— Platk XXXIII. 



Species 87. (Mus. Trevost.) 

 O.STRJEA Peevostii. Ost. tcstd soliild, Tugosd, tmnsrerse 

 oblorujd, arcuatd, subcompre.^sd, intiis versus mar- 

 ginem viridi ; valvd superiori versus marginem 

 viridi, purpurea str-igatd, margine ventrali convexn, 

 plicis majusculis angulatis, imbricatis, ad termi- 

 num viaximis undato, margine dorsali concavo, 

 crenatu ; valvd inferiori albidd, medw-angulatim 

 tumido, plids utrinque dioaricatis acute angulatis. 

 Pi'.i:vost's Ostr^a. Shell solid, rough, transversely 

 oblong, arched, slightly compressed, greenish 

 within towards the margin ; upper valve green 



towards the margin striped with purple, ventral 

 margin convex, undulated with rather large 

 angular, imbricated plaits, very large at the end ; 

 lower valve whitish, angularly tumid in the 

 middle, with divergent, acutely angular plaits on 

 eacli side. 



SOWEIIBY. 



Uab. .' 



Interesting as a second example 

 represented by Oslrtra wcgoddv, 

 known only as a fossil. The specii 

 tion of Dr. Prevost. 



he peculiar form 

 form otherwise 

 is in the collec- 



