42 Proceedings of the Royal Society of Victoria. 



General External Characters. — The flattened body is, as 

 already stated, sometimes over a quarter of an inch in length 

 when full}" extended, but varies from that down to one- 

 eighth of an inch, an average size being three-sixteenths of 

 an inch. The tapering anterior and posterior ends are 

 whitish, and the bulk of the body is of a dark- brown, tinged 

 with red, due to the ova principally. The anterior extremity 

 is somewhat rounded, and has the oral sucker on its ventral 

 face. The posterior end is marked by a distinct, projecting, 

 tail-like appendage, flattened out and rounded posteriorly. 

 It is usually protruded, but may be so retracted as to be 

 entirely hidden underneath. The posterior or ventral sucker 

 is generally relatively smaller than the oral, and with the 

 dark back-ground of the body at this place, often stands out 

 with great distinctness. It is situated somewhat behind the 

 middle of the body. 



The surface of the body is covered with .spines, generally 

 directed outwards or backwards, and sometimes larger than 

 usual on portions of the head end. Towards the posterior 

 end, they are arranged in transverse rows, and curved, with 

 the concave side anterior. Towards the anterior end they 

 seem to be arranged in oblique rows. CJsually, in flattened- 

 out mounted specimens, there are no indications of the spines, 

 while in othei's similarly mounted they stand out with great 

 clearness. 



Alimentary System. — The mouth is situated in the 

 muscular head sucker, not in the centre of.it, but towards 

 the anterior end. Its natural shape is roundish, but may be 

 transversely oval in mounted specimens. It leads into a 

 pharynx, which very soon enlarges into a thickened muscular 

 body, succeeded by a comparatively short gullet, which is 

 thin-walled. The gullet divides into two branches, right 

 and left — the forked intestine — which pass along either 

 side of the body, and terminate not far from its posterior 

 end. The termination may be club-shaped, or even elongated 

 oval, according to the amount of distension. 



Excretory System. — In specimens rendered very trans- 

 parent by caustic potash, the median tube of the excretory 

 system may be seen towards the posterior end of the bodj^, 

 where the reproductive organs do not conceal it. It enlarges 

 considerably here, then tapers to a fine tube which, towards 

 the very end of the body, may be seen to break up into 

 delicate branches. 



