The freshwater fishes of British Guiana, including a study of the ecological grouping of species and the relation of the fauna of the plateau to that of the lowlands . dth of head equal to its length or very little narrower; eye 5 in head, inter-orbital not quite 4; mandibular ramus but little less than interorbital; opercle inthe male (C. M. Cat. No. 1533) with a bunch of graduate bristles, the longest the head, not completely retractile and not hooked; marginal bristle in thesame male three-fourths the length of eye. Bristles scarcely evident in and plates without keels; b
The freshwater fishes of British Guiana, including a study of the ecological grouping of species and the relation of the fauna of the plateau to that of the lowlands . dth of head equal to its length or very little narrower; eye 5 in head, inter-orbital not quite 4; mandibular ramus but little less than interorbital; opercle inthe male (C. M. Cat. No. 1533) with a bunch of graduate bristles, the longest the head, not completely retractile and not hooked; marginal bristle in thesame male three-fourths the length of eye. Bristles scarcely evident in and plates without keels; belly entirely naked; dorsal spine equal to snoutand eye or half eye. Base of dorsal equal to its distance from the caudal, last rayscarcely adnate. Caudal obliquely emarginate; ventrals reaching past origin ofanal; pectorals past origin (to second third) of ventrals. All but the ventral surface brown or slaty, with clear white dots. The alimentary canal in a specimen 100 mm. long is 855 mm. in length. 101. Pseudancistrus nigrescens sp. nov. (Plate XXV, fig. 2.)Pseudancistrus nigrescens Eigenmann, Repts. Princeton Univ. Exp. Patagonia, III,1910, 409 (name only).. Fig. 35. Pseudancistrus nigrescens Eigenmann. Type. C. M. Cat. No. 1539. Type, 182 mm. Amatuk. (Carnegie Museum Catalog of Fishes No. 1539.;Cotype, 149 mm. Amatuk. (I. U. Cat. No. 11960). eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 235 Head about3; depth ; D. 1,7; A. 1,4; plates twenty-four; three or fourpaired plates between the dorsal, eleven behind the anal; width of head almostequal to its length; interorbital in the head, eye ; mandibular ramus the interorbital. Head convex, without ridges or crest; plates of the body not carinate; oc-cipital truncate where it meets the median plate behind it; interopercle with a fewbristles; snout with a swollen margin, sparingly provided with bristles. Dorsal spine a little longer than eye and snout; base of dorsal slightly less thanits distance from the
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Keywords: ., bookauthoreigenman, bookcentury1900, bookdecade1910, bookyear1912
