212 K. MITSUKUKI : STUDIES ON 



Locality :—" Cliallenger " Stat. 164, 169 (Théel '82); Near Ösliima I. 

 (KiSHiNOUYE '94); " Albatross " Stat. 3371, 3431, 3432, 3436 (Ludwig '94) ; 

 " Sil^oga " Stat. 145 (Sluitep '01) ; Sagami Sea. 



Subfamily 2. Elpidiinse. 



Genus Periamma Ieepjer 1896. 



The forms belonging to the family Elpidiicla) seem to be 

 very closely allied and to pass from one to another by gradual 

 transitions. It is therefore no wonder that its genera were not 

 very sharply defined by its discoverer (Theel 1882). So long as 

 the known forms did not increase in number, Theel's classifica- 

 tion was satisfactory enough, aud Lampert (1885) and Ludwig 

 (1889 — '92) followed Theel closely. As soon however as the num- 

 ber of newly discovered species increased, it was evident that 

 Theel's system was not entirely adequate to showing where they 

 belonged. Heeouaed (1902) made an attempt to revise the fami- 

 ly, l3ut he depended altogether on the shape of the body and did 

 not take into account the nature of the spicules, with the result 

 that he gave an entirely new definition to some of the old gener- 

 ic names. Peerier (1902) then proposed a revision of the family, 

 which, while it is not probably the last that will be said on the 

 subject, is a great improvement on Théel and Herouard. I 

 therefore, for the present at least, adopt Perrier's revision, as I 

 have not materials enough at command to attempt one myself. 



