44 î^- <iOTQ. 



In Onclwcotijle, the lif^oks are situated near the extremity of the 

 caudal appendage, between the pair oï .small suckers already described, 

 on the morphologically ventral side (PI. X\^, figs. 1 and 2). They 

 are wholly solid, and are like a fishing hook in shape ; lint the basal 

 end is divided into tw(j processes, one of whicli bears again a rounded 

 process (PL XV, fig. 5). I have not been able to demonstrate any 

 muscular filtres attached to the hooks. 



In TridoiiiiDU, the hooks are situated at the extremities of the 

 posterior l)(jrder of the central polygon of tlie ])osterior sucker, and are 

 provided each with a strong muscle formed by the direct continuations of 

 the longitudinal libres of the body. They are,unlike the h(3oks of most 

 other genera, more (jr less straight (Pis. XX, XXIII, XXIV, XXY). 



In Calicotijlc and Monocolijle, the h(3oks are situated iri tlie 

 posterior radial spokes of tlie posterior sucker on both sides of the 

 median line of tlie body, and project free (3ver the surface of the invest- 

 ing membrane at the margin of the sucker (PI. X^'II, figs. 1 and 2; 

 PI. XIX, fig. 1). They are strongly recur\'ed in both genera. 



In Hcxacoiijle a,nd Octoc. minor, there are two pairs of hooks, of 

 which one is much smaller than the (^clier. They are situated at the 

 posterior end of the body, on Ijotli sides of the inedian line, and 

 between the innermost pair of suckers in Hc'xacot[ilc. In both cases 

 the smaller pair of hooks lie nearer the median line (LM. IX, lig. 7 ; 

 PL Xin, figs. 1, 2, 4, à 5). 



Finally in Epilnlclla, there are three pairs !)f hooks. They are 

 situated on the ventral side of the posterior sucker, and the three pairs 

 are arranged one behind the other ; the most posterior pair Ijeing close 

 to the margin of the sucker. Each hook is provided with a strong 

 bundle of muscular fibres. 



The genera Microcoiijle, Axine, and Diclidopliom are, so far as I 

 have observed, entirely destitute of hooks. 



