. Bulletin of the British Museum (Natural History). Zoology . 72 P. J. P. WHITEHEAD. Fig. 21. Pellona castelnaeana Valenciennes. From Hildebrand 1964 (as Ilisha altamazonica). Dorsal origin equidistant between snout and caudal base ; base of fin invested in low scaly sheath. Pectoral fin tips just reaching base of pelvic fins (left shorter) ; large axillary scale present, 1-71 times in length of fin. Pelvic base almost three eye diameters before vertical from dorsal origin and nearer to pectoral base than to anal origin by two-thirds eye diameter ; triangular axillary scale presen
. Bulletin of the British Museum (Natural History). Zoology . 72 P. J. P. WHITEHEAD. Fig. 21. Pellona castelnaeana Valenciennes. From Hildebrand 1964 (as Ilisha altamazonica). Dorsal origin equidistant between snout and caudal base ; base of fin invested in low scaly sheath. Pectoral fin tips just reaching base of pelvic fins (left shorter) ; large axillary scale present, 1-71 times in length of fin. Pelvic base almost three eye diameters before vertical from dorsal origin and nearer to pectoral base than to anal origin by two-thirds eye diameter ; triangular axillary scale present, 1-56 times in length of fin. Anal origin just below last branched dorsal ray and 2-5 eye diameters nearer to pelvic than to caudal base ; anterior anal rays (up to 7th branched) enlarged and forming a distinct lobe, the remainder of the fin low and even, except slight enlargement of final two rays ; base of fin invested in low scaly sheath 1-5 scale rows in depth. Caudal with rounded lobes, about three- quarters head length. Scales : as in P. flavipinnis. Colour : the entire specimen brown, possibly with the darker markings on pectoral and caudal fins found in P. flavipinnis. Note. Unlike P. flavipinnis, the present species appears to be largely restricted to the Amazon drainage system. The single Guyana specimen described here is from the Rupununi savanna region, an area which is extensively flooded in the rainy season and where the Amazon and Essequibo drainage systems join in wet years in the vast flooded plain known as Lake Amuku (Lowe (McConnell), 1964 : 105). Apart from differences in gillraker and post-pelvic scute counts, P. castelnaeana hardly differs from P. flavipinnis, at least in preserved material. Cervigon (1966 : 130) recorded two specimens from the mouth of the Orinoco (91 and 105 mm ), their gillraker counts being 14 + 27 and 13 + 25. These mast be P. flavipinnis. ODONTOGNATHUS Lacepede, 1800 Odontognathus Lacepede, 1800, Hist. Nat. Poiss., 2 : 220 (Typ
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