162 "ENDEAVOUR" SCIENTIFIC RESULTS. 



Family ALEPOCEPHALID.E. 



The genera Xenodermichthys Giinther, Aleposomus 

 Gill, and Rouleina Jordan are closely allied, but appear 

 to be distinguished as follows: 



A. Gill-openings not extending above the pectorals; mouth 

 small. XENODEBMICHTHYS. 



B. Dorsal and anal fins long, with 33 rays. nodulosus. 

 AA. Gill-openings extending well above the pectorals; mouth 



large. ALEPOSOMUS. 



C. Dorsal and anal fins long, with more than 25 rays. 



Subgenus ALEPOSOMUS. 



Includes copei Gill (syn. socialis Vaillant) and cyaneus 

 Zeugmayer. 



CC. Dorsal and anal fins shorter, with 20 or less rays. 



Subgenus ROULEINA. 



ALEPOSOMUS Gill. 

 Subgenus ROULEINA Jordan. 



Aleposomus Ronle, Bull. Mus. Hist. Nat., 1915. 2, p. 46 

 (guntheri} scnsu lato. 



Rouleina Jordan, Classification Fish., 1923, p. 122 

 (guntheri). 



Rouleina is only subgenerically distinct from 

 Aleposomus, differing only in having shorter dorsal and 

 anal fins. By the kindness of the Director of the Museum 

 d'Histoire Naturelle, I am able to compare my specimens 

 of R. squamilaterus with an example of A. socialis 

 Vaillant (= copei Gill). I find them similar in all larger 

 structural details, though the lateral line is without 

 modified scales in A. socialis. They differ from 

 Xenodermichthys in having the gill-openings extending 

 far above the bases of the pectoral fins and in their 

 larger mouths. A bony stay across the operculum is 

 well developed, which is apparently wanting in 

 Xenodermichthys. 



Key to the Species. 



A. Lateral line indistinct, without scales. 



B. D.15, A. 14. guntheri Alcock. 



BB. D.18, A.17. nudus Brauer. 



AA. Lateral line distinct, with scales. 



C. Pectorals reaching more than half the distance 



from ventrals. lividus Brauer. 



CC. Pectorals reaching less than half their distance 



from ventrals. 

 D. Head 3-7-4-1 in length; D.19-21, A.16-19. 



squamilaterus Alcock 



DD. Head 4-66 in length; D. 18-19, A.17. -icatasei 



Tanaka. 



