294 



ring outward. On the vomer few bluntly rounded teeth in 

 two roundish groups, their own diameter apart, which distance 

 increases when the groups are smaller. Similar teeth in two 

 longish, oval groups on the palatines, nearly touching the 

 vomerine groups. A median longitudinal keel on the palate. 

 10 stiff gillrakers, flattened at their base and separated by a 

 broad, rather high membrane from about 13 stiff but low 

 processes along the hindborder of the gillarch. Dark brown 

 above, white below. Dorsal, adipose fin, caudal, distal part of 

 anal and pectorals and basal part of ventrals dark, anal and 

 ventrals sometimes hyaline. Length 425 mm. 



Habitat: South New Guinea (Lorentz river!). 



In fresh water. 



14. Arius nudidens M. Web. 



Arius nudidens Max Weber, Nova Guinea IX, livr. 4. 1913, p. 538. 



B. 9; D. I. 7; A. 19; P. I. II 12; V. 6. 



Elongate; height under dorsal spine 5 3 / 5 6, head more 

 than 3, its width i 3 / 4 1 4 / 5 in its length. In adults the dorsal 

 profile gently sloping down in a straight line to the broad, 

 flat, rounded snout, which goes 2*/ 2 times or somewhat more in 

 the head and projects so much before the lower jaw that the broad 

 band of teeth in the upper jaw is completely exposed. Gape 

 rounded, more than 2 times in head; lips strongly thickened 

 at corner of mouth. Headshields corrugate, occipital process 

 about i l h times longer than broad at base, sharply keeled 

 in young ones, less so in adults, its sideborders convergent, 

 rounded behind and touching the crescentic basal bone of 

 dorsal spine. Median fontanel short and shallow. Rough humeral 

 process short but broad. Eye with incomplete orbital ring, 

 directed somewhat upwards, g l j 2 ii 4 / 5 in length of head, 

 2 J / 2 4 J / 2 in the slightly convex interorbital space. Maxillary 

 barbels extending to base of pectorals, mandibulary ones on pec- 

 torals, mental ones about a half shorter. All barbels are ribbon- 

 shaped, less so in young ones, where they are relatively 

 shorter. Height of dorsal equal to head without snout, its 

 flattened spine with serrated front and hindborders equal to 

 postorbital part of head, one eye-diameter longer in young 

 specimens. Base of well developed adipose fin much longer 

 than that of dorsal, about 2 times in its distance from last- 

 named. Anal with the hindborder concave, its greatest height 



