276 ASAJIRO OKA; ON SOME NEW 



members of a genus separated, more or less widely, from all the genera 

 of land leeches that had been then defined. 



They decidedly form deviations from the generally accepted rule, 

 that in GnathohdeUida', each unabbreviated somite consists of five 

 rings. We know, indeed, at present, thîuiks to the untiring re- 

 senTches of Dr. R. Blanchard of France, one genus of Gnatltohdellidce 

 which has only three rings in a complete somite, and two others from 

 the Family, HerpohdelUdce (Syn. Neplielidœ), which have respectively 

 six and eight rings in a somite. Moreover, some specimens of Trocheta 

 from the Crimea were found to have as many as eleven rings in each 

 complete somite. Such being the case, the leeches I am going to 

 describe ;ire not the only instances, in which a somite consists of a 

 number of rings other than five. What is striking in them, however, 

 is that the number of rings in a. complete somite is not even con- 

 stant within the limit of the genus, though constant in each species. 

 Besides, these new land leeclies exhibit many other peculiarities, 

 so that an account of them should certainly not be without interest 

 both to systematists and to those investigat(jrs who are occupied with 

 the external morphologv of the order Hirudinea. 



I take the opportunity here of expressing my heartiest thanks to 

 Prof. Mitsukuri tor atfording me various conveniences for investiga- 

 tion and to Prof, [jima for kindly placing at my disposal a specimen 

 out of his own collection. For a number of specimens I am indebted 

 to Prof. Nakagawa of Ivumamoto, who collected them for me during 

 his stav anion o^ the Nikko mountains. 



So far as I am aAvare, tliere are only five well established genera, 

 of the Order Hirudinea, whose members are exclusively terrestrial, viz. : 

 Hcemadijjsa, Xewhdella, Mesohdella, C ijlicohdella and Luinhricohdella. 



