1922.] 



A. Oka : Hirudinea from the Inle Lake. 



533 



XXIV 



five-ritlged somite of Hirudo or Herpobdella (Nephelis) the first 

 two rings of Trocheta correspond with the first ring of these 

 leeches, the two broad rings with the second and third, the two 

 narrow rings that come next with the fourth, and the last three 

 narrow rings with the fifth. As shown in the accompanying 

 figure, the narrow rings are not all of the same width, the seventh 

 and eighth of each somite being always somewhat narrower than 

 their neighbours either in 

 front or behind. These 

 rings have, in all pro- 

 bability, been derived by 

 subsequent division from 

 the anterior half of the 

 last ring of a five-ringed 

 somite and are, conse- 

 quently, each equivalent 

 to one-fourth of the ori- 

 ginal ring, while all the 

 other narrow rings are 

 each equivalent to one 

 half of the original ring. 

 In larger specimens of 

 Trocheta from Japan these 

 relations can be demons- 

 trated so perfectly as to 

 leave no doubt about the 

 matter. The subject will 

 be discussed more fully 



in my paper on the Herpobdellidae of Japan to be published 

 shortly. 



I refrain from giving the exact number of rings in these 

 specimens, as it was impossible to count them in some places. 

 On the whole, the annulation appears to be very similar to that 

 of Japanese species of the same genus. 



Text-fig. 7. — Trocheta quadrioculata, sp. nov. 

 Somites xxiv-xxvii, with sucker : x 25. 



Remarks upon the genus Scaptobdella Blanchard. 



In my Synopsis of Japanese Leeches (13) I recognized the 

 genus Scaptobdella Blanchard and described a new species under the 

 name of Scaptobdella blanchardi. Subsequent studies, however, led 

 me to cast doubts upon the validity of this genus, which I now 

 regard as synonymous with the European genus Trocheta. The 

 reasons for this change will be given in my future paper referred 

 to above. M. P. Gedroye, in his paper on European leeches (7) 

 expressed his doubts as to the systematic value of the genus Scap- 

 tobdella, and in his Synopsis of Polish Leeches (8) published some 

 years afterwards, he abolished that genus and placed Scaptobdella 

 horsti, the type of the genus, in the genus Trocheta naming it 

 Trocheta horsli. In this regard I am of exactly the same opinion 

 as the Polish author. 



