Fishes of the Western North Atla?itic 347 



Description. Proportional dimensions in per cent of extreme breadth of disc. Male, 

 364mm broad, from Key West, Florida (U.S.Nat. Mus., No. 125797). Female, 

 527 mm broad, from Pernambuco, Brazil (Harv. Mus. Comp. Zool., No. 246). 

 Bisc: vertical length 86.2, 85.5. 



Snout length: in front of orbits 18.4, 17.1; in front of mouth 20.3, 18.6. 

 Orbits: horizontal diameter 8.0, 5.7; distance between 9.3, 8.0. 

 Spiracles: length 7.1, c^.'^\ distance between 17.0, 14.2. 

 Mouth: breadth 8.2, 8.9. 



Exposed nostrils: distance between inner ends 10.7, 10.4. 

 Gill openings: lengths, ist 3.0, 2.7; 3rd 3.0, 2.7; 5th 2.3, 1.9; distance between 



inner ends, ist 18.6, 19.4; 5th 11. 4, 11. 9. 

 Pf/i'/V^; anterior margin 17.0, 15.6. 



Distance: from tip of snout to center of cloaca 78.8, 74.1 ; from center of cloaca 

 to origin of caudal spine 37.1, 33.8. 



Disc about 1.2 times as broad as long (specimens i 5 to 60 in. wide), rhomboid; 

 tip of snout subangular, projecting at most only a little or not at all; maximum anterior 

 angle in front of spiracles about 135°; anterior margins varying from nearly straight 

 to slightly concave or weakly convex anterior to level of eyes, becoming increasingly 

 convex toward outer corners, the latter being either abruptly rounded or subangular; 

 posterior margins nearly straight anteriorly but becoming weakly convex posteriorly; 

 posterior corners abrupt, much as in D. centroura\ inner posterior margins straight or 

 weakly convex. Axis of greatest breadth about 38— 4070 of distance rearward from 

 tip of snout toward rear limits of disc. Tail moderately depressed dorsoventrally and 

 evenly rounded laterally anterior to spine; its upper surface posterior to spine with a 

 low fleshy keel extending rearward nearly or quite as far as rear termination of lower 

 tailfold on most specimens, but rounded on some;*^ lower surface of tail with a more 

 or less conspicuous longitudinal fold originating about under origin of tail spine and 

 extending rearward for a distance about 1.2— 1.4 times as long as distance from axils 

 of pectorals to spine; nearly uniformly wide throughout most of its length but nar- 

 rowing at either end to merge with general contour of tail; its maximum width at 

 spine about equal to or greater than height of tail on some large specimens, but only 

 about half as high as tail on others and on embryos. Tail from center of cloaca 1.9 (small 

 specimen) to 2.3 times as long (large specimen) as distance from center of cloaca to 

 tip of snout, if not damaged; distance from origin of tail spine to center of cloaca about 

 45 "/o as long as distance from cloaca to snout. 



Length of free portion of tail spine (one only on specimens seen) about as great 

 as distance between outer margins of orbits; total length of spine from origin about 

 1.3 times that great; its lateral teeth 52 and 80 on each side in two specimens counted,^* 

 often covered with skin to tip even on large specimens. 



45. We have examined one such specimen. 



46. These spines were not damaged. The specimen whose tail spines had 52 teeth was 36 inches wide, the one with 

 80 teeth was 60 inches wide. 



