52 THE VOYAGE OF H.M.S. CHALLENGER. 



Aegieonichthys aj^j^elii. 



Aegseonichthys appelii, Clarke, lor. cit., pL vi. 



D. 5. A. 4. C. 8. P. 17. 



The cephalic spine consists of a tuft, one-sixth as long as the fish, with a swollen 

 muscular base and a hemispherical head, from which spring three or four long branched 

 tentacles ; the shaft is covered with minute spines. Greyish, mottled with light and 

 splashed with dark brown. 



The hemispherical head of the cephalic spine is described as a capsular gland, the 

 front of which is covered with a silvery or nacreous integument, with an aperture in the 

 centre communicating with the interior and surrounded by a black ring. It is evidently 

 the same structure which I have described in Ceratias hisj^uwsus, and adapted for the 

 same function. It is phosphorescent, and probably illuminates the play of the tentacles 

 which serve to allure other creatures. 



Ceratias, Kroyer. 



Pediculates without ventral fins and with two gills and a half only ; no pseudo- 

 branchite. Head very large ; body and tail short ; eyes small. Mouth large, with the 

 mandible projecting. Jaws armed with a series or narrow band of depressible teeth of 

 various lengths. Skin with dermal scutes or spinelets. The spinous dorsal fin reduced 

 to one or two spines, which are generally modified into tentacles, and sometimes 

 provided with an accessory luminous a})paratus. The soft dorsal and anal short. 



The species may be arranged in the following order : — 



I. Two cephalic spines — Ceratias [Diceratias) hispinosus. 



II. One cephalic spine. 



A. A second spine on the back, with lateral caruncles ; no vomerine teeth— 



Ceratias (Ceratias) holholli. 



B. No spine on the back ; with caruncles. 



1. Caruncles placed at a distance from the soft dorsal. 



a. Two caruncles only; no vomerine teeth — Ceratias (Mancalias) 



uranosco2yiis. 

 h. Three caruncles; vomerine teeth? — Ceratias {Typhlopsaras) 



shujl'ldti. 



2. Caruncles placed immediately in front of the soft dorsal. 



a. Terminal cephalic joint very short — Ceratias ( ) 



caru7iculatus. 



b. Terminal cephalic joint long — Ceratias [Cnjptopsaras) couesii. 



