2 THE NAUTILUS. 



ADULA CALIFORNIENSIS Philippi. 



Modiola californiensis (Esch. ms. ) Philippi, Zeitschr. Mai. for 

 1847, p. 113. California, Eschscholtz. 



Adula stylina Carpenter, Rep. Brit. Assoc. for 1863, p. 644, 

 1864 ; Ann. Mag. Nat. Hist., 3rd ser., vol. 14, p. 425, Dec. 

 1864 ; Smithsonian reprint, p. 237, 1872. Neeah Bay, Wash. 



Modiola (Lithophagus) schmidtii Schrenck, Amurl. Moll., p. 

 500, pi. 21, figs. 4-7, Oct. 1867. West coast of Sakhalin Island, 

 Sea of Tartary. 



Adula californiensis Dunker, Conch. Cab., neue Ausg., viii, pt. 

 3, Lithophaga, p. 22, pi. 5, fig. 19, 1882 ; Index Moll. Mar. 

 Japan, 1882, p. 227. 



Distribution. Neeah Bay, Wash, to San Diego, Cal., North- 

 ern Japan and the Sea of Tartary. 



This species is shorter than A. falcata, and destitute of the 

 of fine transverse surface sculpture which in the latter recalls 

 that of some species of Lithophaga. It is slender, with the 

 radial ridges rather emphasized and the shell substance has 

 usually more or less dark bluish coloration. 



The posterior dorsal area (where it has not been cleaned off 

 by a collector or dealer) has a more or less velvety pile, such 

 as is often found on Modiolas, underneath which the peri- 

 ostracum has a brilliant polish. The umbones in the adult are 

 invariably eroded. The Japanese specimens, received from 

 Hirase, are quite identical with those from California. 



ADULA DIEGENSIS Dall. 



Modiolus diegensis Dall, NAUTILUS, xxiv, No. 10, Feb. 1911, 

 p. 110. San Diego, Cal. (young shells). 



Distribution. San Francisco Bay to San Diego, and Cape 

 St. Lucas. 



The young specimens of this species are apparently free-living 

 and have less of the arcuation found in the last species, which 

 is a borer. 



The adult shell has the posterior portion much more capa- 

 cious than in A. californiensis, nearly twice as wide and high as in 

 specimens of the latter of the same length. The color seems 

 variable. The young shells described by me were dark bluish, 



