1922.] A. Oka : Hirudinea from the Inle Lake. 529 



The nervous system agrees most closely with that of Glossi- 

 phonia stagnalis. 



Annulation. Somites i, ii, and iii are uniannulate. Somite 

 iv is biannulate, consisting of an anterior broad and a posterior 

 narrow ring; it is in the hinder half of the broad ring, i.e. ring 4, 

 that the four anterior eyes are transversely arranged, while the 

 remaining two eyes are imbedded in the interior of the next ring. 

 Somites v and vi are biannulate, with the rings of practically 

 equal breadth. Somites vii-xxiv are triannulate ; here the rings 

 are of the same breadth throughout, so that there is no distinction 

 between the inter-somital and interannular furrows. Somites xxv 

 and xxvi are biannulate with the anterior ring about twice as 

 broad as the posterior. Somite xxvii has but one ring, behind 

 which is placed the anus. At the posterior extremity, where the 

 somites are abbreviated, the somite boundaries can be deter- 

 mined without difficulty, as it is always the first and second annuli 

 that are fused. 



This species can be easily distinguished from all other species 

 of the genus by the peculiar arrangement of the eyes mentioned 

 above. 



Placobdella parasitica, juv. (?). 



Syn. : Hirudo parasitica, Say, 1824. 



Clepsine parasitica, Diesing, 1850. 

 CI. plana, Whitman, 1891. 



Locality : — Canal on W. side of Inle Lake. One specimen, 

 on Tata shanensis (Kobelt). 



It is with much doubt that I assign this specimen to the 

 above species. Judging from the size as well as from the condi- 

 tion of the genital pores, it is certainly immature, and it is diffi- 

 cult to ascertain whether the slight but obvious discrepancies 

 existing between this specimen and typical P. parasitica are due 

 to difference in age or to specific distinctness. 



The specimen is a good deal contracted. The form is oval, 

 much arched dorsalty, concave ventrally. The head is curved 

 downward, so that the eyes cannot be seen when the animal is 

 viewed from above. The lateral margins are similarly inflexed. 

 The total length measured along the curved dorsum is 5'5 mm., 

 the transverse diameter 3 mm., the widest part being a little 

 behind the middle of the body. The posterior sucker is circular 

 and measures about 1 mm. across ; its margins are inflexed. 



There is a single pair of eyes in the anterior half of the third 

 annulus. They are not so close together as in the normal speci- 

 mens of Placobdella parasitica. As I could not study the unique 

 specimen in sections, it was impossible to determine whether the 

 eyes were really simple, as they appeared to be in surface view, 

 and not composed of three eyes crowded together as is the case 

 in that species. 



The genital pores are separated by two rings. The male 

 opening is situated in the furrow between rings 27 and 28, the 



