ON TEMNOCEPHALA. 281 



Temnocephalse ; arid I have since found that other species 

 of this remarkable genus infest the fresh-water crayfishes of 

 the rivers of New South Wales. 



I must here acknowledge my indebtedness to various friends, 

 through whose kindness I have been able to procure ample 

 supplies of specimens, more especially to Mr. Alexander Morton, 

 of Hobart; Mr. E. C. Merewether,and Mr. Harry Merewether, 

 of Bondi and Mount Wilson ; Mr. Alexander Hamilton, of 

 Mudgee ; Mr. J. D. Cox, of Mount Wilson ; Mr. Charles 

 Chilton, of Dunedin, and Mr. J. J. Fletcher. 



General Description of Temnocephala. 



Temnocephala (PI. XX, figs. 1 — 5) is a leech-like animal, the 

 largest about half an inch in length. In outline the body is 

 ovate or pyriform, but much compressed from above down- 

 wards; the anterior end narrower than the posterior, and the 

 lateral border fringed with a narrow, delicate fold. At the 

 narrower anterior end there is, in the middle, in the case of 

 the Tasmanian species, a rounded, dorso-ventrally compressed 

 lobe, about a fifth of the length of the rest of the body, and on 

 either side of this two very long and slender tentacles, which 

 are filiform, and a half to two thirds of the total length of the 

 body when fully extended, but are capable of being greatly 

 retracted. In the case of the New South Wales species, and 

 that from New Zealand, there are five equal slender tentacles. 

 Close to the broader posterior end on the ventral aspect is a 

 very large sucker of circular outline supported on a short stalk. 

 Near the middle Hue of the dorsal surface, placed near together 

 a little behind the bases of the tentacles, is a pair of small 

 black eyes. On the ventral surface, not far from the anterior 

 end, is the mouth — a well-marked aperture. Some distance 

 behind it, a little way in front of the sucker, is the common 

 genital aperture — a short transverse slit leading into the genital 

 cloaca. 



By incident light against a dark ground, the body of the 

 larger New South Wales species (fig. 2) and of the Tasmanian 



