GENUS — CONCHODERMA. 139 



Maxilla, about -f- ths of the size of the mandibles, step- 

 formed, with five steps generally distinct ; at the upper 

 angle there are two large unequal spines, of which the 

 lower one is the largest, with a third long thin one on 

 the first step ; lower spines doubly serrated. Apodeme 

 directed inwards and backwards. 



Older Maxillce (PL X, fig. 16) simply arched; the 

 membrane of the supra-cesophageal cavity under these 

 maxillae is highly bull ate and villose. Olfactory orifices 

 not prominent. 



Cirri, — First pair not seated far distant from the 

 second pair. The three posterior pair have the anterior 

 faces of their segments considerably protuberant, support- 

 ing four or five pairs of long bristles ; between which, 

 there is a row of minute, fine, upwardly pointing bristles : 

 on the lateral upper margins of each segment, there are 

 a few very minute spines ; dorsal tuft short, with thick 

 and thin spines intermingled. In the first cirrus (of 

 which the rami are nearly equal in length), and in the 

 anterior ramus of the second cirrus, the faces of the seg- 

 ments are highly protuberant, and clothed with thick 

 transverse rows of finely and doubly serrated spines : the 

 anterior ramus of the second cirrus is considerably thicker 

 than the posterior ramus, which latter, together with 

 both rami of the third cirrus, differ from the three pos- 

 terior cirri only in the intermediate and in the lateral 

 marginal spines being slightly more developed. 



Caudal Appendages, absent. 



Alimentary Canal. — The upper part of the stomach has 

 four large caeca, of which the posterior one is the largest ; 

 the whole surface, also, is covered with minute pits, 

 arranged in transverse rows. 



Generative System, developed to an extraordinary de- 

 gree. The testes run into all the filamentary append- 

 ages, as well as more or less, into the pedicels of the 

 cirri : the two vesicular seminales unite tvithin the penis, 

 either just beyond its basal constriction, or up one third 

 of its length. Penis short, hairy. The ovarian tubes not 



