1917.] NATURAL SCIENCES OF PHILADELPHIA. 327 



is very short and concave. The outer lip arches well forward in the 

 middle. 



Length 3.4, diam. 0.9, length of aperture 1mm.; 5| post-nuclear 

 whorls. 



The slender figure, the narrow form of the aperture and the glossy- 

 surface give this little shell a superficial likeness to the genus Stromhi- 



formis. 



VI. THE OSTREID^. 



Of the four species of Ostrea known from the islands, two are 

 apparently extinct. The existing species are quite small oysters. 

 0. sandvichensis is common on stone and shell bottom in Pearl 

 Harbor. 0. hanleyana appears to inhabit open shore and reefs. 



Professor Bryan- has recorded the unsuccessful attempts to 

 introduce eastern and Californian oysters. It could not reasonably 

 be expected that oysters from waters so much colder would thrive, 

 and so far as is known, they have died out completely. There is a 

 large valve of the Virginia oyster in the Bryan collection, picked out 

 of material dredged in Honolulu Harbor, probably a ballast shell. 



Ostrea sandvichensis Sowerby. PL XXI, figs. 4 to 8. 



1871. Ostrea sandi'ichensis Sowerby, Conch. Icon. Vol. 18, PI. 27, fig. 66 



(Sandwich Islands). 

 1916. Ostrea rosacea Bryan, Natural History of Hawaii, p. 457, PI. 104, 



fig. 8. 



Oahu: Eastern Lech (Pilsbry), Ford's Island and Waipahu (Bryan), 

 in Pearl Harbor, fossil at the latter place. Honolulu Harbor (Bryan). 



Kauai: Lualualei ba.sin, Milolii, fossil (Bryan). 



Molokai: Kainalu (Bryan). 



This fluted oyster is abundant in Pearl Harbor. It rarely exceeds 

 a length of 35 or 40 mm., and is usually smaller. It varies from 

 rounded to subtriangular in contour. The attached valve is generally 

 strongly plicate at the free edge. The other valve may be strongly 

 plicate, but is often nearly smooth. In color it varies from dull 

 purple to pale fleshy, with or without purple rays or clouds. The 

 nterior is whitish or olive. There is more or less minute crenulation 

 near the hinge. The valves are of the same size, or the lower one 

 may project very slightly beyond the other. The specimens growing 

 on Trochus sandwichensis imitate the sculpture of the gastropod 

 (fig. 8, Ford's Island). Figs. 4 and 5 are from examples taken in 

 the Eastern Loch. 



A fossil form from Ford's Island, Pearl Harbor is heavier and in 



- The Natural History of Hawaii, p. 445. 



