EIGENMANN: the freshwater fishes of BRITISH GUIANA 287 



Dorsal inserted slightly behind the vertical from the insertion of the ventral; 

 pectorals reaching half-way to second third of ventrals; ventrals half-way to base 

 of last anal ray; adipose fin over middle of last anal ray. 



Light brown above, bordered below by a black band from tip of snout and 

 mandible to the end of the lower caudal lobe; the band is widest on the caudal 

 peduncle, where it unites with its fellow of the other side; a bar connects the two 

 lateral bands in front of the anal. Lower parts silvery white. Dorsal hyaline; 

 lower caudal lobe black, obliquely crossed near the center by a red band, and mar- 

 gined with red above; usually a black ocellus-like spot or streak near the middle 

 of the caudal rays near the center of the fin; middle, and sometimes the posterior 

 anal rays, dark. Opercle purple. 



Archicheir Eigenmann. 

 Archicheir Eigenmann, Ann. Carnegie Mus., VI, 1909, 46. 



This genus is a Nannostomus with peculiar pectorals. In Nannostomus the 

 pectorals are normal, as in related genera ; in this genus they appear to have retained 

 the embryonic structure. They are broad, dermal flaps, with hair-like fringes. 



Gill-membranes united, free from the isthmus. 



144. Archicheir minutus Eigenmann. (Plate XXXVII, fig. 5.) 

 Archicheir minutus Eigenmann, Ann. Carnegie Mus., VI, 1909, 46; Repts. Prince- 

 ton Univ. Exp. Patagonia, III, 1910, 428. 



Type unique, 26 mm. Canal at Christianburg. (Carnegie Museum Catalog 

 of Fishes No. 1186.) 



This species is readily recognizable by the color of the caudal and anal fins. 



Head 3.5; depth 5.66; D. 9; A. 11; scales large. Eye 3.5 in the head, con- 

 siderably greater than the interorbital, but little shorter than the snout. 



Origin of dorsal a little posterior to origin of ventrals. Adipose fin considerably 

 behind tip of the anal. 



Back chocolate. A light band from end of snout to base of superior caudal 

 lobe; a dark band from end of maxillary to the base of the inferior caudal lobe. 

 A black spot at base of the pectoral, and one before the first ventral ray. Dorsal 

 dusky; adipose black. Middle caudal rays black; an oblique 'bar from the edge 

 of base of each lobe to the end of the median black bar, the lowermost one much the 

 widest, the superior bar brown, shading into black at both ends. Anal hyaline, 

 a black bar across tips of its last rays. 



It is very probable that the pectoral fin in this si)ecimcn is abnormal, and that 

 the genus is a synonym of Poecilobrycon. 



