THE AMERICAN TETRAGONOPTERINAE. 125 
1. GyYMNOCORYMBUS THAYERI Eigenmann. 
Plate 11, fig. 2. 
Gymnocorymbus thayert E1GENMANN, Bull. M. C. Z., 1908, 62, p. 93 (Tabatinga to Gurupa); Rept. 
Princeton univ. exped. Patagonia, 1910, 3, p. 437. 
HapitatT.— Amazon. 
Specimens examined. 
Number of 
Catalogue number specimens Size in mm. Locality Collector 
19242 type 1 40 Tabatinga Bourget 
20706 2 54 Teffé Agassiz 
19272, 20973 4 30-56 Cudajas Thayer & Bourget 
20804 1 70 Manacapuru James 
20807 9 50-77 
20998, 21065 20 40-50 Silva, Lake Saraca Thayer 
20984 29 38-57 Serpa Thayer 
20710, 20720 4 50-62 Villa Bella Agassiz 
20789 22 44-58 Santarem Bourget 
21007 8 45-55 José Fernandez Cotinho 
20724 2 65-72 Gurupa Agassiz 
21001 7 44-54 Jose Fernandez Cotinho 
Head 3.5 on an average; depth 1.7 on an average, ranging from 2.1 to 1.4; 
D. 11; A. 34-41', most frequently 38 or 39; scales 7 to 8-33 to 36-8 to ventrals; 
eye 2.25-3, 2.65 on an average; interorbital slightly less than the eye in the 
young, slightly more than the eye in the adult. 
Very deep and very much compressed; the ventral profile much more arched 
than the dorsal, its deepest point at the origin of the anal; dorsal profile depressed 
over the eyes, humped in front of the dorsal; preventral area narrowly rounded 
in cross-section, postventral area more narrowly compressed; predorsal area 
narrowly rounded. 
Occipital process one third or somewhat less the distance from its base to 
the dorsal; occipital fontanel continued to the tip of the occipital process as a 
groove, parietal portion sometimes partly arched over and demarked from 
the occipital groove; frontal fontanel about half the length of the occipitai, 
its anterior end over the anterior margin of pupil; the profile beginning to 
1 Of sixteen counted one has thirty-four anal rays, two thirty-five, one thirty-six, one thirty-seven, 
four thirty-eight, five thirty-nine, one forty and one forty-one. 
2 Of twelve counted four have thirty-three anal rays, one thirty-four, five thirty-five and two thirty- 
six. 
