FISHES OF THE GULF OF MAINE 



75 



Fionas 32. — Sting ray (Dasyatis centroura), male, about 55^ inches wide, Woods Hole, Massachusetts, and tubercle from 

 tail, about 0.7 times natural size. From Bigelow and Schroeder. Drawings by E. N. Fischer. 



long as from its own origin to the cloaca; the 

 upper side of the tail is rounded, except for a low 

 ridge close behind the spine (or spines). The 

 spear-pointed tail spines, of which there are 1, 2, 

 or sometimes 3, are situated well back on the tail. 

 One spine that we examined had about 40 saw 

 teeth on each edge. 



Young ones are smoo th skinned (except for the tail 

 spines) . Larger ones develop 1 to 3 irregular rows 

 of conical tubercles along the midline of the disc, 

 with others on the shoulders as well as on the 

 outer posterior part of the disc, and the tail be- 

 comes very rough finally, with conspicuous thorns 



along its whole length on its upper side, and 

 rearward from abreast of the tail spines on its 

 lower side. The lower side of the disc is smooth. 



Large specimens are easily distinguishable from 

 other sting rays of our Atlantic coast by their very 

 thorny tails and by the large tubercles on the 

 outer parts of their discs. Small ones on which 

 the thorns and tubercles have not yet developed, 

 are recognizable by the shape of the disc, com- 

 bined with the presence of a skin fold on the lower 

 side of the tail but none on the upper side. 



Size. — This appears to be the largest sting ray 

 of the western North Atlantic. The greatest 



