S T R ^ A. 



Plate IV. 



Species 6. (Mus. Cuming in Brit.) 



OsTRfiA CALLOCHROA. Ost. tesfd suhorhiculo/ri, com- 

 pressd, solidd, valvis mbceqiialibus ; valvd supe- 

 riori vix convexd, purpurea alboque-luteo radiatd, 

 eoncentrice depresso - lamellatd ; valvd injeriori 

 moderate convexd, plus rainusve jnirpureo tinctd, 

 costis obtusis radiantibus armatd, intiis albd, mar- 

 gine squaniifero subpurpureo ; maryinibus latera- 

 libus prope umbones distincte deniiculates.. 



The fine-coloured Ostii^a. Shell suborbicular com- 

 pressed, solid, valves nearly equal, upper valve 

 very little conve.x; rayed with purple and yellow- 

 ish white, concentrically flatly laminated; lower 

 valve moderately convex, more or less tinted 

 with purple, armed with obtuse radiating ribs ; 

 white within, margin scaly purplish ; lateral 

 margins distinctly denticulated near the umboes. 



Hanlet. Pro. Zool. Soc. 1845. 



Hah. Chili. 



Species 7. (Mus. brit. • 



OstRjBa hyotis. Ost. testd irregulariter mbquadratd, 

 solidd, spinis tuhiformibus, super angulos plicarum 

 magnarum septem circa extanlibus armatd, fusco- 

 viridi; auriculis svhcompressis, foliaceis pliciferis ; 

 intus lalefusco marginatd. 



The htodoid Ostr^l\. Shell irregularly subquadrate, 

 solid, armed wth tube-shaped spines standing out 

 iipon the angles of about seven large folds; 

 greenish brown ; auricles rather compressed, 

 foUaceous plicated ; widely bordered with brown 

 inside. 



LINN.EUS. Systema Naturje. 



Hab. Indian Ocean. 



The colouring of this shell is rather peculiar, being 

 of a imiform greenish brown, and the deep angular 

 plaits are surmounted generally with tubular spines. 



October, 1870. 



