346 



fossato-emarginata, radialim sulcato-costata, costis numerosis, 

 inequalibus argute muriculata ; intus albido-incarnata. Long. 

 1| ; alt. I ; lat. If poll. Hob. New Zealand. 



Of the same type as P. Islandicus^ but is small, more convex, 

 and the sculpture coarser ; the groove separating the auricle 

 from the body of the shell is remarkably deep. 



OsTREA ciRCUMSUTA. T. solida, elongata, ovata, cinerea, ine- 

 quivalvis, marginibus undulatis : valva superior denticulis radian- 

 tibus marginalibus in foveis sub-marginalibus valvse inferioris 

 aptantibus : area cardinal is triangularis, contorta, longitrorsum 

 fossata : interior alba, limbo violacescente. Long. 1^ ; lat 1 poll. 

 Hob. Feejee and Samoa Islands. 



The distinctive characters are the denticles, about twice as 

 long as broad, around the entire margin, tinged with violet. In 

 young specimens the purple coloring is wanting. 



OsTREA MORDAX. T. pctrosa, angusta, lunata : valva inferior 

 concava, digitis triangularibus erectis fuscescentibus marginata : 

 valva superior minor, planulata, margine profunde sinuato et gran- 

 ulato, sinibus cum digitis coaptantibus : interior albida, olivaceo- 

 maculata ; cicatrice elongata, valde incrassata, nigra : area cardi- 

 nalis planulata, lata. Long. 2 ; lat. 1 poll. Hah. Feejee Islands. 



The horizontal digitations of the upper valve fitting into the 

 erect canine teeth of the lower valve, together with the denticles 

 within, and the black elevated cicatrix, may serve to identify this 

 species. The upper valve fits so deeply and so closely into the 

 lower that it is nearly impossible to separate them without 

 fracture. 



OsTREA GLOMERATA. T. crcsccntica, lata, sinistrorsum arcu- 

 ata, solidiuscula, planulata, scabriuscula, laminis dentatis prope 

 marginem foliata, nigricans et albo-radiata ; margine undulato : 

 interior alba ; fovea apicali profunda ; cicatrice nigricante ; mar- 

 ginibus aut simplicibus aut lineolatis et prope cardinem granula- 

 tis ; limbo corticali purpureo et viridi variegate. Long, et lat. 2 

 poll. Hob. New Zealand. 



This may possibly have been described, though no figure or 

 description answers to the specimens I have seen. 0. spathulata 

 and denticulata correspond most nearly. The deep umbonal pit 



