A NEW PEARL (lYSTER FROM THE HAWAIIAN ISLANDS 



By Paul Bartsch 



Curator of MoUusks and Cenozolc Invertebrates. United States National 



Museum 



The explorations of the Pearl and Hermes reefs and the waters of 

 Oahn. Hawaiian Islands, last summer by Dr. Paul S. Galtsoff, of the 

 United States Bureau of Fisheries, yielded a lot of material which 

 plainly shows that the large pearl oyster of these regions is not 

 Piiictada cumingi Reeve as usually considered, but a new species, 

 which I take pleasure in naming for Doctor Galtsoff, who has trans- 

 mitted his material to me for identification. 



PINCTADA GALTSOFFl, new species 



Plates 1 and 2, figures 1, 2, and 3; figures 7 and 8, type 



Description. — Shell large, varying in shape from irregularly 

 ovate to subquadrate, rather compressed. Hinge oblique, rather 

 short and deep; bj^ssal notch of the right valve deeply infolded. 

 The outside of the shell is much laminated. In old shells, like the 

 type, these laminations do not show the fimbriations at the free 

 border present in young individuals. The outside is covered by a 

 yellowish-olive periostracum. The nacre of the inside is lustrous 

 silver}^ pearly gray, with a bluish tinge sometimes bordering on 

 l)urple near the edge in old shells, as in the type. The outer margin 

 in the type is yellowish horn-colored. In young specimens a band 

 near the edge of the nacreous portion maj^ be gold green with a 

 greenish tinge or smoky with a greenish suffusion and decidedly 

 irridescent. The marginal border in young individuals may be 

 brown, variegated with radiating bands of darker brown or the edge 

 may be quite deeply smoke gray or almost sooty black. Adductor 

 muscle scar large, a little paler than the rest. 



Type.—TYiQ type, U.S.N.M. No. 282426, comes from tlie Pearl and 

 Hermes reefs, and measures: Altitude, 288.0 mm.; length, 233.0 mm.; 

 thickness, To.O mm. 



No. 2878.— Proceedings U. S. National Museum, Vol. 79, Art. 12. 



04870—31 1 



