Fishes of the IVestern North Atlantic 



381 



about under origin of tail spine, its rear termination varying from about under rear 

 termination of upper fold to a point posterior to latter by a distance about half as great 

 as length of upper fold; length of tail from center of cloaca about 1.8—2.3 times as 

 great as distance from center of cloaca to tip of snout in embryos and about 1.8 times 

 after birth if intact. 



One or two tail spines, or perhaps more, the replacement spine developing ante- 

 rior to the older one on specimens seen ; when fully developed, maximum length of free 

 portion of spine (or spines) is about 50-60 "/o ^s great as, and total length from origin 

 about equal to, distance between outer margins of orbits; greatest breadth of spine 



Figure gi. Dasyatis say. A Tip, B Middle and C Cross section of 

 middle of tail spine of male, 615 mm wide, from Rio de Janeiro (Harv. 

 Mus. Comp. ZooL, No. 989), about 2.5 X. D Upper left-hand tooth 

 band of same, about 1 .6 X . E Upper right-hand tooth band of female, 

 991 mm wide, from Rio de Janeiro, Brazil (Harv. Mus. Comp. ZooL, 

 No. 991), about 1.3 X. 



5.5—6 */o ^s great as its total length; 60 lateral teeth on each side on specimen counted, 

 their outer cutting margins arcuate. 



Upper surface of disc and tail of young specimens, up to about 220 mm wide, 

 smooth except for tail spines; a row of small to medium tubercles, with median crest 

 sloping anteriorly, soon appearing along midline of back, first over pectoral girdle, next 

 forward to nuchal region, then rearward onto tail nearly to spine; also 1—2 on each 

 shoulder, the one anterior to the other. With growth this median row is replaced ante- 

 rior to pectoral girdle by 2—3 irregular rows of smaller rounded tubercles; 1—2 shorter 

 rows of large tubercles develop on each shoulder, and the midrow becomes less regular 

 in spacing posterior to pectoral girdle with the loss of individual tubercles, especially 

 in females, until on some mature specimens only two large conical ones remain near 

 the tail spine. Median belt of head anterior to eyes more or less roughened with small 

 prickles on some large specimens, as are outer posterior parts of disc on some at matu- 

 rity; pelvics smooth in both sexes, but margin of upper tailfold and upper and lateral 

 sides of tail rearward from midpoint of upper fold more or less prickly on large speci- 

 mens. Lower surface of disc and of tail and lower tailfold smooth at all stages in growth. 



