24 S. GOTO. 



XII, fig. 4, c'). Somewhat similar but shorter pieces (d) lie in pairs 

 at the peripheral end of h. A short spine-like piece (e) lies opposite 

 the process of the piece c with its pointed end directed towards the 

 piece d. These last-mentioned pieces, the pieces d, and the peripheral 

 portions of the pieces a and c are imbedded at the very margin of the 

 fibrous wall of the sucker (PI, XII, fig. 4). 



In tfae natural position of the suckers these chitinous pieces are, 

 in most species, placed in such a way that the leg of the T-shaped 

 piece is directed towards the median line of the body in the anterior 

 suckers, while in the posterior suckers it is directed obliquely forward 

 (PI. X, fig. 5). In Diclid. tetroAonis, however, the same piece is 

 directed forwards in the posterior three pairs, but backwards in the 

 foremost pair. This difference of arrangement of the pieces of the 

 chitinous framework in the foremost pair of suckers is a curious 

 exception to the rule. 



Each of the four quadrants into which the wall of the sucker is 

 divided, presents in radial sections an oval or semicircular mass, con- 

 sisting, as in the species already described, of prismatic fibres travers- 

 ing its whole thickness at right angles to its free surface (PI. XII, 

 fig. 4). The four quadrants are separated from each other in the centre 

 by an intervening mass of connective tissue, in which is imbedded the 

 central part of the T-shaped piece («) already described^ 



The free surface of each quadrant is covered with a thick cuticle 

 which is locally chitinized in short staff-shaped pieces arrangied in 

 series. Each series of these staff-shaped chitinous portions is, in a 

 surface view, roughly speaking somewhat semicircular (PI. XII, fig. 2), 

 with the open side directed towards the centre of the sucker. In fig. 

 1, PI. XII, the series have been a little displaced by pressure. To- 

 wards the mesenchyma the wall of the sucker is bounded by a thin, 

 cuticular membrane. Around the outer margin of the sucker the 



