107 



concolore, atro-purpureo aut ruhro-purpurascente, undigue sub- 



lamellosd, ad margines dense plicatd ; lamellis imbricatis, confertis, 



depressis ; plicis regularibus, rotundatis ; valvis in longitudine 



paribus ; inferiore profundd, superiore planulald atgue in costas 



planas suleis latis remotis radiatim divisd; superficie internd 



albidd, ?nargine interno denticulato ; denticulis elongatis ; cicatrice 



satis magnd, obovali aut suborbiculari. Long. 2 poli. 



Hab. Isle of Luzon; on rocks (Cuming). Mus. Cuming, Walton. 



In typical specimens the shell is subtriangular, from the anterior 



side sloping in a produced and straightish line, abruptly from the 



beaks. The sculpture is both elegant and peculiar, the extremely 



depressed ribs being divided by rather broad grooves, and assuming 



a scalloped appearance at their edges, from the crowded sublamellar 



imbrications which cover the entire surfade. 



OsTREA BicoLOR. Ost . testd obovatd, nunquam elongatd, subtenui 

 aut solidiusculd, subcompressd, vix lamellosd, purpureo-fuscescente 

 radio uno vel radiis duobus albidis ornatd ; margine simplici ; 

 natibus subacutis ; superficie internd, albidd colore externo margi- 

 natd ; cardine denticulis nullis munito. Long. 2^ poli. 

 Hab. Senegal ? Mus. Cuming, Hanley. 



As the few specimens I have yet examined of this elegant species 

 have been attached by the entire surface to the sheathing of vessels, 

 I am unable to describe the characteristics of the lower valve. The 

 lamellae, when existing, are flattened, so that the shell presents a 

 smooth surface, and appears inclined to expand laterally whenever 

 unobstructed in its growth by adjacent substances. 



OsTREA CoLUMBiENsis. Ost. testd subincEcuivalvi, subtenui, lamel- 

 losd, albidd, purpureo radiatd, subcompressd; valvuld inferiore 

 magis convexd; superficie internd albidd, snbmargaritaced ; car- 

 dine denticulis nullis munito; cicatrice satis magnd, reniformi. 

 Long. 2 poli. 

 Hab. St. Elena, West Columbia, adhering to rocks at half-tide 

 (Cuming). Mus. Cuming. 



AU the specimens I have seen are attached by the entire surface 

 of the lower valve. The shape varies from oblong to suborbicular, 

 and the valves are of equal length, but the shelly substance of the 

 shallow upper valve fits into the lower one, and is only continued to 

 the margin by the lamellse, which, when the habitat permits, branch 

 nto wavy foliations. 



OsTREA Callichroa. Ost. tcstu obovatd aut suborbiculari, solidius- 

 culd, subeeguivalvi ; valvuld superiore jiurpureo albogue lutescente 

 radiatd, concentrice lamellosd ; lamellis depressis ; valvuld inferiore 

 magis minusve purpureo tinctd, cosiiscue radiantibus subobtusis 

 dense armatd; superficie internd, albd ; ?nargine simplici; cardine 

 denticulis distinctis munito. Long. 2 poli. 

 Hab. Island of Chiloe, adhering to stones at low-water mark 

 (Cuming). Mus. Cuming. 



The general appearance is that of our edible oyster, but the colour- 

 ing is magnificent. 



