224 Proceedings of the Royal Society of Victoria,. 



Of the muscles of the jaws there are tliree sets (Fig. C.) 



A. Transverse or circular (Figs. 11, 13, C). 



These lie beneath the cuticle, and, except for this 

 thin membrane, form the outei-most layei' of the 

 jaws. These muscles are absent only where the 

 cuticle is thickened to form the ridge along which 

 the teeth and glands occur. They are really a 

 continuation of the circular muscles of the pharynx 

 on to the jaws. 



B. Longitudinal (L.) 



Beneath the transverse are situated the longitudinal 

 muscles continuous with the longitudinal of the 

 pharynx and forming a single layer on the jaws, but 

 increasing in size and number of layers where they 

 are attached to the pharynx. At this point some 

 fibres pass into the body wall but the majority run 

 on to form the large mass of muscles on each side of 

 the pharynx gradually merging into the body wall. 



C. Dorso- Ventral (H.) 



These pass through the jaw from the dorsal to the 

 ventral side, forming its main support. They are 

 seen just beneath the free projecting ridge and cease 

 to exist only at the base of the jaw, where it springs 

 from the pharynx wall. 



On account of the number and arrangement of the jaws, the 

 bite from this leech is a longitudinal slit. 



