40 PERCY SLADEN TRUST EXPEDITION 
Tasmania and differ from the rest in the possession of but two jaws, a peculiarity shared 
by Idiobdella seychellensis. 
The appearance of a new species possessing this remarkable characteristic of the 
Australian land-leeches renders advisable the sub-division of the Hzemadipsine into the 
following two series : 
Series 1. Vrignathofere. With three jaws, one supero-median and two infero- 
lateral. The bite inflicts the familiar y-shaped incision. 
Including the genera Hamadipsa, Xerobdella, Phytobdella, Plano- 
bdella and Mesobdella. 
Series 2. Duognathofere. With two jaws, the supero-median member being 
absent. The bite inflicts a nearly straight cut. 
Including the genera Moquimia, Philemon, and Idiobdella (described 
below). 
It is to Moquima, with its typical or ‘“‘ complete 
Idiobdella is most nearly related, since the ‘“ complete 
ry) 
somite formed of five rings that 
” somite in Philemon is but 
four-ringed. 
[Moquinia is synonymous with the Geobdella of Whitman, 1886. The latter name 
however, having been applied by de Blainville to Trocheta in 1828, justified the proposal 
of the former name by R. Blanchard in 1888*. The first adequate description of the 
Australian land-leeches was given by Miss Ada M. Lambert in 1897, 1898. ] 
After the number of the jaws, the most striking character presented by Idiobdella 
consists in the position of the genital orifices. 
Apathy (1888) laid it down as an axiom that in all leeches the male opening occurs 
in somite XI and the female in somite XII (somites X and XI, as counted by Whitman), 
but it would have been more correct to have stated that these orifices occur within the 
limits of these somites, since in Helobdella stagnalis the genital ducts open by a common 
pore between them. 
Even now, however, this statement admits of an exception, for in J. seychellensis the 
male opening is situated in somite X and the female in somite XIII, an occurrence unique 
among leeches. 
The reproductive organs in the new species do not differ materially from those of 
Philemon and Moquinia except in regard to the testes. Of these, only nine pairs exist 
in I. seychellensis and the reduction has taken place anteriorly ; the anterior pairs show 
a marked and progressive diminution in size, whilst the pair corresponding to the foremost 
pair in allied species 1s absent. 
The female apparatus as a whole, and also the much coiled epididymes, are bulky in 
comparison with the size of the animal, and this probably bears some relation to the 
unusual position of their respective external openings. 
* Article “ Hirudinea” in Dictionnaire Encyclopédique des Sciences Médicales, Paris, 1888. 
+ “The Structure of an Australian Land Leech” (Philemon), Proc. Royal Soc. of Victoria, Vol. x. (1897), 
p- 211; also “ Description of two new Species of Australian Land Leeches” (Geobdella), loc. cit: Vol. xi. (1898), 
p- 156. 
