190 Transactions. — Zoology. 



Of internal anatomy I can only note that the alimentary 

 •canal is similar to that of the medicinal leech, since I have 

 not as yet examined the other organs. 



The most characteristic feature about this new species is 

 the existence of three fleshy folds concealing the jaws. If the 

 mouth, or oral sucker, be viewed from below three semi- 

 circular ridges are seen, one transversely disposed — ventral 

 ridge — the other two being obliquely placed, and meeting in 

 the median dorsal line. These folds may be termed -''lips," and 

 correspond to structures which occur, indeed, in Hirudo medici- 

 nalis (with which alone I have had an opportunity of comparing 

 them by personal observation), but are quite feebly developed 

 and inconspicuous. In our native leech, on the other hand, 

 they are so prominent as to be mistaken at first for the jaws, 

 but that they are arranged in the wrong way. Microscopic 

 examination, however, shows that they are highly vascular in 

 structure and hood-like in form, each being concave towards 

 the median plane and convex externally, with a thickened free 

 margin. 



On turning these aside, or by cutting away the ventral 

 "lip," the true jaws are exposed in the usual position — viz., 

 a median dorsal jaw and a pair of latero- ventral jaws — 

 alternating, therefore, with the " lips." But the form of the 

 jaws differs from that of other species of Hirudo (so far as 

 I am aware) in that they are not semicircular, with the basal 

 axis longer than the vertical axis. On the contrary, in 

 H. antipodum the vertical axis is greater than the basal axis, 

 the median {i.e., oral) margin is nearly straight, and the outer 

 margin convex. Further, there is practically an absence of 

 denticles, such as occur in the other species of the genus. 

 Nevertheless, the oral margin has its cuticle raised into a series 

 of irregular rounded prominences, which appear to be due to 

 oblique foldings of the cuticle, and these are arranged in a 

 single series. But, although practically edentulous, we have 

 the evidence of Mr. Dunlop that the jaws are sufficiently armed 

 to pierce the human skin. 



So different are these jaws from other species of Hirudo 

 that one is tempted to make a new genus for our species ; but 

 as in all other external features, at any rate, this species 

 agrees with other species of the genus Hinido I have con- 

 sidered it better to leave it in this genus till I have worked 

 out the internal anatomy, and especially after reading Whit- 

 man's remarks (loc. cit., p. 366) on the ^ev\\x9.Hcevwpis, wliich 

 he includes within the genus Hirudo, since the only character 

 in which the two genera differ lies in the less number of den- 

 ticles in the former: " In view of the great variability in the 

 number of denticles not only among different species of one 

 and the same genus, but also among different individuals of 



