Fishes of the IVestern North Atlantic 



367 



of tail along median third of its length, tapering toward its posterior end to merge 

 gradually with lower surface of tail. Upper surface of tail with a low cutaneous ridge 

 originating about under tip of tail spine and extending rearward about three-quarters 

 as far as lower tailfold. 



Tail spine (only one on specimens examined) about 1.2 times as long from its 

 origin as distance between outer margins of orbits, its free portion about 80 "/o as long; 



Figure 87. Dasyatis guttata, upper tooth band (above) and lower 

 tooth band with oral papillae (below) of immature male pictured 

 in Fig. 86, about 1.3 X. 



its breadth about 7 "/o ^s great as its total length; 26 lateral teeth on each side on speci- 

 men counted (255 mm wide), the outer cutting edges obtusely angular. 



Skin, apart from tail spine, smooth on embryos and probably on newborn speci- 

 mens; but 3—4 tubercles developing soon after birth over pectoral girdle and 2—3 on 

 anterior part of tail, the series soon becoming continuous from nuchal region back to 

 a little in advance of tail spine; the tubercles largest over pectoral girdle and on base 

 of tail; those over pectoral girdle heart-shaped in dorsal aspect, those rearward with 

 narrow median crest sloping anteriorly but vertically truncate posteriorly; each shoulder 

 with two large tubercles on some small specimens but not on larger individuals. Smaller, 

 blunt, heart-shaped tubercles appear also along the midbelt of the disc from the time 

 the breadth has reached 300 mm, developing sparsely between the orbits but closely 



