144 CONCHODERMA AURITA. 



calcareous matter, continuous sheets of chitine are spread 

 out beneath it; hence, during the disintegration of the 

 outer surface, the carina comes to project more and more, 

 and at last drops out ; subsequently, even the little hole 

 in which it was imbedded, disintegrates and disappears. 



Peduncle, cylindrical, distinctly separated from the 

 capitulum, and generally twice or thrice as long as it : 

 the thickness of the outer membrane generally great, but 

 variable : surface of attachment variable, either pointed, 

 or widely expanded, or formed into divergent projections. 



Filamentary Appendages, seven on each side, highly 

 developed, long and tapering ; there are two beneath the 

 basal articulation of the first cirrus, and one on the poste- 

 rior margin of the pedicel of each cirrus, excepting the 

 sixth pair ; the filaments on the pedicels are nearly twice 

 as long as the cirri themselves. 



Mouth, — mandibles, with the five teeth nearly equi- 

 distant, and towards their bases finely pectinated on both 

 sides ; inferior angle rudimentary, often represented by a 

 single minute spine : in one specimen, there were only 

 four teeth on one side. Maxillae, with fiye steps, not very 

 distinct from each other, with the first step much curved. 

 The larger of the two upper great unequal spines is 

 pectinated, like the teeth of the mandibles; there is a 

 third long finer spine beneath the upper large pair. 



Cirri rather short, broad, with the anterior faces of 

 the segments protuberant, especially those of the first 

 cirrus and of the anterior ramus of the second pair : spines 

 on the anterior cirri doubly serrated. Posterior cirri, with 

 the intermediate spines between the pairs, long ; dorsal 

 tufts, minute. On the lower segment of the pedicels of the 

 four posterior cirri, there are two separate tufts of bristles. 



Colours extremely variable ; sometimes five longitudinal 

 bands of dark purple can be distinctly seen (as in C. vir- 

 gatd) on the peduncle, these bands becoming more or less 

 confluent on the capitulum ; at other times, the capitulum 

 is more or less spotted, or often nearly uniformly purple : 

 the sack, cirri and trophi are, also, purple. 



