60 triopidjE. 



clavate and retractile, and the clubs lamellar; the labial 

 appendages are dilated and stellate, with crenate lobes; it is 

 a native of the China Sea. 



Genus ATAGEMA, Gray, 



Tentacles clavate, the apices truncate and adorned with 

 cirrhi. Mantle with an elevated longitudinal crest on the 

 middle of the back. Gills very small, at the end of a dorsal 

 sac. 



Ex. A. carinata, Quoy and Gaimard, pi. 64, fig. 1. 



The mantle in this genus extends considerably beyond the 

 foot posteriorly ; the tentacles are retractile within sheaths, 

 and there is an elevated ridge or longitudinal crest along the 

 upper part of the back. 



Fam. TKIOPID^E. 



Teeth, many in each cross series (rarely only four), the 

 inner lateral ones large, irregular- shaped. Mantle small, 

 edged with tentacular appendages; gills on the middle of 

 the hinder part of the back, in a common cavity, sur- 

 rounding the vent; vent dorsal. 



In this family the body is somewhat angular, and the 

 mantle is distinct and furnished with tubercular appendages ; 

 the species of the genera comprising this group constitute 

 some of the most delicate and beautiful forms of Nudibran- 

 chiate Mollusks. 



Genus triopa, Johnston. 



Teeth, central none, lateral 8 8. Tentacles clavate, 

 pectinated, retractile within simple sheaths ; forehead pa- 

 pillose. Gills, few, pinnate, placed around the vent. 



