Fishes of the Western North Atlantic 365 



Dasyatis guttata (Bloch and Schneider) 1801 

 Figures 86, 87 



Study Material. Eighteen specimens, 210 to 710 mm broad; nine embryos, 108 

 to 133 mm broad, eight with small yolk sac still attached and one with umbilical scar 

 only; all from Rio de Janeiro and vicinity, Para, and Marajo Island at the mouth of 

 the Amazon River, in the collection of the Harvard Museum of Comparative Zoology. 

 Distinctive Characters. Thanks to its projecting snout, D. guttata differs widely in 

 appearance from all other long-tailed Sting Rays of the western Atlantic except D. 

 sabina and Z). geijskesi. The much more abruptly rounded outer corners of the disc set 

 Z). guttata of all sizes apart from D. sabina, the shape of disc and pelvics from D. 

 geijskesi (cf. Fig. 86 with 85). The blunt and close-set tubercles that clothe the midzone 

 of its disc are also diagnostic for Z). guttata, except for young specimens. 



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

 455 mm broad, from Para, and female, 710 mm broad, from Rio de Janeiro, Brazil 

 (Harv. Mus. Comp. Zool., Nos. 573 and 993 respectively). 

 Disc: vertical length 90.0, 93.0. 



Snout length: in front of orbits 22.6, 25.1 ; in front of mouth 24.9, 26.3. 

 Orbits: horizontal diameter ^.^, 4.9; distance between 11.4, 13.0. 

 Spiracles: length 5.9, 6.2; distance between 14.1, 16.2. 

 Mouth: breadth 7.5, 8.7. 



Exposed nostrils: distance between inner ends 9.0, 9.4. 

 Gill openings: lengths, ist 2.9, 2.5; 3rd 2.9, 2.8; 5th 1.8, 2.0; distance between 



inner ends, ist 15.9, 20.0; 5th ii.o, 12.5. 

 Pelvics: anterior margin 15.8, 18.2. 



Distance: from tip of snout to center of cloaca 78.7, 84.3; from center of cloaca 

 to origin of caudal spine 43.0, 43.1. 



Disc rhomboid, about i . i times as broad as long, both in small specimens and in 

 larger; snout with blunted tip, projecting conspicuously from the general contour in 

 subtriangular form; maximum anterior angle in front of spiracles about 105—115°; 

 outer anterior margins of disc slightly convex toward outer corners but weakly concave 

 anterior to level of eyes; outer corners abruptly rounded to subangular, forming approx- 

 imately a right angle; posterior corners more broadly rounded; posterior margins 

 weakly convex, increasingly so toward posterior corners; inner margins moderately 

 convex. Axis of greatest breadth about 50 "/o of distance rearward from tip of snout 

 toward posterior limit of disc. Tail from center of cloaca about 2.5 times as long as 

 distance from center of cloaca to tip of snout,^"* moderately compressed laterally, oval 

 in cross section anterior to spine, approximately round from spine back to tip; its sides 

 without ridges, but lower surface with a well developed cutaneous fold originating 

 about under origin of spine and extending rearward for a distance about 1.25 times as 

 long as distance from origin of spine to cloaca ; its width about ^/s-^/s as great as height 



104. Often damaged. 



