22 S- OotO. 



The muscular, fibres of the postxjrior suckers are attached to 

 the median chitinous piece of the posterior wall near the bottom 

 of the suckers (PI- II, fig. 7). They are divided into a few 

 bundles, and are directly continuous with the longitudinal fibres 

 of the body, 



Octocotyle, Qiclidophora, and Hexacotyle — The anterior suclcers 

 of these three genera present nothing specially different from those 

 of Axine and Microcotyle, and I shall therefore pass them oyer, 

 merely referring the reader to the figures (PL IX, fig. 8; PI. X, 

 fig. 6 ; PI.- XIII, figs. 1 & 4). I shall, however, note that in 

 all these, there is no membranous septum, that in Diclidoplwra- (Pi. 

 X, fig. 6) some of the fibres of the internal bundle of muscle of one 

 side cross over to the sucker of the other side, and lastly that in 

 Hexacotyle the suckers are exceedingly small. The posterior suckers 

 are, however, very different in the three genera, so that they will be 

 treated separately. 



Posterior suclcers — In Octocotyle the four pairs of posterior suckers 

 are arranged merely along the ventro-lateral border of the hind- 

 most part of the body, so that the caudal disc is, as already mentionedj 

 directly continuous with the body proper. Each sucker is somewhat 

 bean-shaped, and is raised a little above the general surface of the 

 ventral side (PI. IX, figs. ], 4, «& 7). The anterior and posterior 

 walls are very thick, and consist of prismatic fibres just as in Microco- 

 tyle and Axine. The chitinous framework consists of a simple basal 

 piece (PI. IX, figs. 3 & 10, a) and a pair of marginal pieces (fc), both 

 imhedded in the substance of the wall. The basal piece is nearly 

 straight and bears at each end a short process which makes a right 

 angle with it, and is directed towards the mouth of the sucker. The 

 marginal pieces are U-ghaped and are imbedded in the substance of 

 the anterior and posterior walls along their viery margins, so that each 



