Fishes of the Western North Atlantic 163 



Alopias suferciliosus (Lowe), 1840 



Big-eyed Thresher 



Figures 25, 26 



Study Material. Young male, 1,296 mm. in total lengthy two embryos, 64 mm. and 

 632 mm. long} jaws of 18-foot specimen (Harv. Mus. Comp. Zool.) 5 all from the north 

 coast of Cubaj° also photographs of embryos from Salerno, Florida." 



Distinctive Characters. This species is set apart from the Common Thresher, the only 

 Atlantic Shark with which it might be confused, by the following features: its relatively 

 enormous eye, longer snout, the tip of its first dorsal fin overlapping the pelvics, its second 

 dorsal terminating considerably in advance of the anal and only 10 or 11 teeth on a side 

 in each of its jaws (about 20 in the Common Thresher). 



Remarks. The original description of suferciliosus was limited to the statement that 

 it is "at once distinguished from the only other known species of the genus, Carcharias 

 vulpes, Cuv., by the enormous eye and its prominent brow."" But the size of the eye is 

 so striking a character that the specimens described here can safely be referred to Lowe's 

 old species. 



Description. Proportional dimensions in per cent of total length. Male embryo, 632 

 mm., from Cuba (Harv. Mus. Comp. Zool., No. 36155). Male, 1,296 mm., from Cuba 

 (Harv. Mus. Comp. Zool., No. 36090). 



Trunk at origin of pectoral: breadth 5.8, 7.4; height 8.2, 9.1. 



Snout length in front of: outer nostrils 4.3, 4.6} mouth 7.4, 6.0. 



Eye: horizontal diameter 4.1, 2.8. 



Mouth: breadth 4.6, 4.4; height 3.0, 2.6. 



Nostrils: distance between inner ends 1.9, 1.8. 



Labial furrow length: upper part 1.9, 1.95 lower 0.7, 0.5. 



Gill opening lengths: ist 2.1, 2.9; 2nd 2.5, 2.95 3rd 2.4, 2.8; 4th 2.1, 2.2; 5th 



1.8, 1.9. 



First dorsal fin: vertical height 5.2, 5.2; length of base S-Sy 6.3. 



Second dorsal fin: vertical height 0.6, 0.7; length of base 0.8, 0.9. 



Anal fin: vertical height 0.8, 0.9; length of base i.i, i.O. 



Caudal fin: upper margin 48.7, 49.1 ; lower anterior margin 6.3, 6.3. 



Pectoral fin: outer margin 20.4, 19.1; inner margin 4.3, 3.8; distal margin 17.2, 



18.1. 



Distance from snout to: ist dorsal 33.3, 31.2; 2nd dorsal 45.3, 46.O; upper caudal 



51.3, 50.9; pectoral 20.1, 17.O; pelvics 37.2, 36.5; anal 48.2, 47.8. 



Interspace between: ist and 2nd dorsals 8.9, 8.9; 2nd dorsal and caudal 5.4, 4.6; 



anal and caudal 1.6, 1.9. 



9. Contributed by Luis Howell-Rivero. lo. Contributed by Stewart Springer. 



II. Lowe, Proc. zool. Soc. Lond., 8, 1840: 39. 



