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



Pteroidonus, n. gen. 



The lower pectoral rays are incompletely united with the upper part of the fin and are 

 prolonged. Body elongate, compressed, covered with small scales; lateral line incomplete, 

 close to the dorsal profile. Head oblong, thick, covered with scales. Eye small. 

 Vertical fins united, but the narrow caudal projecting beyond the short anal and dorsal 

 rays. Ventrals reduced to a simple filament, inserted behind the humeral symphysis, 

 and somewhat distant from each other. Snout broad with rounded profile, including 

 the lower jaw, without barbel. Mouth wide ; bands of vUliform teeth in the jaws, on 

 the vomer and palatine bones. Operculum with a straight spine ; praioperculum armed. 

 Eight brauchiostegals. Gill-laminjB rather short ; gill-rakers rather long, lanceolate and 

 widely set ; pseudobranchise none. 



A true deep-sea form. 



Pteroidonus quinquarius, n. sp. (PI. XXII. fig. B). 



B. 8. D. 99. A. 87. C. 5. V. 1. P. 15 | 5. L. transv. ca. 35 (above vent). 



Body elongate, compressed, its depth being less than the length of the head, which 

 equals the distance between the vent and root of pectoral fin. The tail tapers almost to 

 a point. Head not much deeper than broad, its depth being equal to the length of its 

 postorbital portion ; it is flat above, the interorbital space being more than twice as 

 broad as the eye. Eye small, without orbital fold, much shorter than the snout, and 

 about one-seventh of the length of the head ; it is lateral, but situated immediately below 

 the upper profile of the head. No spines about the orbit. Nostrils rather distant from 

 each other, open ; the posterior, the larger, immediately in front of the upper part of the 

 eye, the anterior close to the end of the snout. 



Snout broad, rather depressed, overlapping the lower jaw. Mouth wide, somewhat 

 oblique, the much dilated posterior extremity of the maxillary extending backwards 

 beyond the orbit. Prajorbital region narrow ; intermaxillary styliform. Teeth in villi- 

 form bands, the bands of the vomer and palatines very narrow ; vomerine band A-shaped. 

 Prseoperculum with a rounded angle which is armed with three very short and weak 

 spines ; opercular spine moderately strong and straight. 



The bones of the head are thin, with shallow muciferous cavities. Nearly the entire 

 head, even the dilated extremity of the maxillary and the glossohyal region, are covered 

 with small scales. Gill-membranes entirely separate. 



The dorsal fin commences at a short distance behind the root of the pectoral, is rather 

 low, the rays being enclosed in a scaly skin at the base, and has its last and shortest 

 rays connected with the caudal by membrane. The anal is vqtj similar to the dorsal, 

 but lower. The length of the very narrow caudal is two-fifths of that of the head. 



