10 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 120 
Although proportional measurements were made on all three species 
of Pterophyllum, the great variability even at nearly equal sizes 
suggests that little reliance can be placed on measurements for iden- 
tification purposes. 
Tapie 4.—Character index: Total number of rays in dorsal and anal fins added to 
number of scale rows for Pterophyllum 
Species and localities 83 85 87 89 91 93 95 97 99 101 103 105 107 109 111 113 115 117 119 121 123 125 
84 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 122 124 126 
altwm 
Upper Rio Orinoco oy iy, Eh 
scalare 
British Guiana Leh Bot ee 5 
Upper R. Araguaia 
Belém; Marajo I. 
Pérto do Moz 5 
Santarém; Obidos, 
Villa Bella; R. 
Cupari; Porto 
Negro; Monte Alegre Sea Sees lies eal 
Manaus; R. Urubu; R. 
Purus; Manacapurt; 
Coary By hy Als th a) a ube al 
Tefé 1 Pa 6 
Tonantins; R. Jutahy; 
R. Solimées; Taba- 
tinga il 983 
Peruvian Amazon Bey ey aly 83 
dumerilii 
British Guiana 1 
Rio Negro-Amazon 2 3 Py al 1 
Rio Negro (type of 
leopoldi) 1 sky Le Srl at 
Mouth of Amazon, 
Cacaual 1 1 
to we OO 
_ 
bo 
i 
= 
= 
be | 
cn 
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on 
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bo 
bo 
An inspection of tables 3 and 4 indicates that for P. scalare there 
may be certain areas where distinct populations exist; the specimens 
from Pérto do Moz, Santarém, Obidos, for example, average fewer 
soft dorsal fin rays than specimens from Manaus, Rio Urubu, and 
Tefé. Specimens from British Guiana have about the same counts 
as those listed from Pérto do Moz. Before any conclusion can be 
made for the “population” at the mouth of the Amazon, large series 
will need to be studied to find out the meaning of the bimodal nature 
of the frequency distribution for specimens from Belém and Marajé 
Island. 
P. scalare ranges in the Amazon Basin and in the Rupununi and 
Essequibo Rivers of British Guiana with a single record from French 
Guiana (MNHN 221-61-3-10), the exact locality unknown. The 
known localities represented by specimens studied by me are recorded 
in plate 1. 
U.S. GOVERNMENT PRINTING OFFICE: 1967 
