Bept..i9».] YENDO.-yOTES OX ALGuE NEW TO JAPAN. Ii. 2G7 



it is almost pure, giving a bright grass-green colour to the 

 inner side of the shells. The colour is deepest along the mantle 

 line fading gradually toward the umbo. The muscular impres- 

 sions are always free from the alga. 



Locality. Misaki (Prof. N. Yatsu) : Hiroshima ( Prof. X. 

 Ohno) : Otaru Bay (!). Apparently common. 



Distribution. Pacific side of North America, Alaska to Van- 

 couver Island : Atlantic coast of the United States, Greenland, 

 West Indies and Europe. 



Derbesia tenuissima Crouan. 



Flora Finistr. p. 133-J. Agardh ; Till Alg. System. VIII, p. 33. 

 = Derbesia marina Soliek. Ann Science Nat. 1847. p. 158. PI. 

 9, fig. 1-17. 



After studying the specimens of Derbesia in the Agardhian 

 Herbarium at Lund and in the Herbarium of the Trinity Col- 

 lege, Dublin, I am strongh' inclined to identify my specimen 

 with the species above mentioned. A specimen sent from Solier 

 under Derbesia marina is found in Dublin and with this ray 

 specimen agrees especially well. It is to be understood, how- 

 ever, the difference between D. tenuissima Crouax and D. 

 vaucheriasformis J. Ag., so far as the specimens in the Agardh- 

 ian Herbarium show, is not so sharp as to be expected from 

 the key in Till Algernes Systematik VIII. The mode of ramifi- 

 cation in both species seems to be often variable. As my 

 specimen is sterile, the determination is provisional. 



Xo specimen of Derbesia has ever been recorded from the 

 Asiatic side of the Pacific Ocean. On the American side, D. 

 marina Kjellm. is assigned to the coast from Alaska to Cali- 

 fornia. It is rather interesting to find the present species, 

 which is hitherto known from the Mediterranean Sea only, 

 within our boundary. 



Locality. Misaki: a few specimens have been collected 

 there by myself in 1903 but never again. Apparently a " guest". 



Distribution. Mediterranean Sea. 



