16 



W. G. MDEWOOD. 



The red line of the shield which is so conspicuous and constant a feature of 

 Cephalodiscus does not seem to be present in Rhabdopleura. Schepotieff shows, in 

 the exact position occupied by the red line in Cephalodiscus, a " Pigmentstreif " (1904, 

 pi. 2, fig. 9, and 1905, p. 796, fig. 1), but since he says nothing about red colour, one 

 is led to conclude that the pigment-stripe is black. The crowd of black pigment spots 

 at the anterior point of the shield of Rhabdopleura, assumed to be a rudimentary organ 

 of vision, finds no equivalent in Cephalodiscus. The relations of the shield to the 

 mouth, however, and the great mobility of the shield, and the glandular nature of 



TEXT-FIGURE 8. Rhabdoptoira narmani, a polypide greatly enlarged. (Copied from Lankester, 13, plate 38, 



fig. 1.) 

 a, mouth ; 6, anus ; c, polypide stalk ; d, buceal shield ; c, plume ; /, visceral mass. 



the thick central part of the ventral wall of the shield (Schepotieff, 1905), are the 

 same in both Rhabdopleura and Cephalodiscus. 



The collar region is produced in both into a postoral lamella and plumes. The 

 latter are two in number in Rhabdopleura, and although Cephalodiscus has in most 

 cases four pairs or more, Harmer's discovery of male polypides of C. sibogae with one 

 pair of plumes only (10, p. 84) is of interest in this connection, in spite of the fact 

 that such plumes do not possess pinnules. 



