299 



Dorsal and ventral profile convex, somewhat less so in very 

 small specimens. Height 2.1 — 2.9, 2.8 — 3.7 in length with caudal. 

 Head 3.4 — 3.8, 4 — 4.5 in length with caudal. Eye 2.7 — 3.2, 

 equal to or somewhat more than snout, 1.2 — 1.3 in postor- 

 bital part of head, which is equal to or slightly longer than 

 interorbital space. Lower jaw somewhat prominent. Mouth- 

 opening not reaching quite to vertical through frontborder of 

 eye. Lips not thickened, except somewhat at symphysis of 

 jaws. Very small teeth in several rows on jaws, extending on 

 outside of lips on vomer and (?) on palatines. Tongue smooth. 

 One row of scales on suborbital part of cheeks. Operculum 

 with large scales excepting the superior ones, which are small. 

 Dorsal separated by 14 — 16 scales from occiput. Spine of first 

 dorsal equal to or slightly longer than postorbital part of 

 head, longer than spine of second dorsal, which is again longer 

 than anal spine. Origin of anal opposite to that of first dorsal. 

 Length of base of anal longer than distance between origin 

 of first dorsal and end of second dorsal. Pectorals somewhat 

 shorter than head without snout. Scales smooth or with faint 

 crenulations at their hindborder. Caudal peduncle longer than 

 high in small specimens, as high as long in larger specimens. 

 Colour of preserved specimens brownish, darker above. A 

 faint narrow blackish longitudinal band is sometimes visible. 

 Fins dusky. In some specimens the second dorsal and the anal 

 have a red marginal band and the ventrals are also tinged 

 with red. Length 61 mm. 



Habitat: North New Guinea (Mamberamo-river !), collected 

 by Jhr. W. C. VAN Heurn. 



Note. A remarkable pecularity of this species is, that the 

 elevated rhombic form is attained at a much smaller size than 

 in all other species of Melanctacniinae known to us. 



2. Rhombatractus vanheurni n. sp. 



D'.L4— 5; D-. L 18—21; A. L 24— 26; P. L 13— 14; V. L5; 

 L.l. 38 — 40; L.tr. 12-13. 



Dorsal and ventral profile evenly convex in the young, when 

 older the back is more arched and the greatest convexity of 

 the ventral profile more forward, so that the form of the fish 

 is more rhombic. Height 2.7^ — 3.2, 3.1 — 3.9 in length with 

 caudal. Head 3.4 — 3.7, 4.1- — 4.3 in length with caudal. Eye 

 3.4 — 4.8 in head; 1.2 (in small specimens) to nearly twice 



