Fishes of the Western North Atlantic 401 



473 mm wide, from Barnegat, New Jersey (U. S. Nat Mus., No. 104909). Male, 

 1,208 mm wide, from Woods Hole, Massachusetts (U. S. Nat. Mus., No. 85956). 

 Disc: length 49.3, 49.5. 



Snout length: in front of orbits 7.6, 7.0; in front of mouth 10. i, 9.1. 

 Orbits: horizontal diameter 3.2, 2.0; distance between 7.4, 7.7.^^ 

 Spiracles: length 3.8, 3.8; distance between 8.9, 8.7. 

 Mouth: breadth 9.1, 9.4. 



Exposed nostrils: distance between inner ends 6.6, 7.0. 

 Gill openings: lengths, ist 2.2, 2.3; 3rd 2.2, 2.2; 5th 1.2, 1.2; distance between 



inner ends, ist 17.5, 16.0; 5th 11.8, 11.7. 

 Pelvics: anterior margin 7.2, 8.1. 

 Distance: from tip of snout to center of cloaca 44.2, 45.5; from center of cloaca 



to origin of caudal spine 9.1, 8.0. 



Disc about twice as broad as long or a little more (about 2.0—2.1 times), its anter- 

 ior angle (tip of snout to level of anterior margins of orbits) about 135° in specimens 

 measured, thus somewhat more obtuse than in G. micrura (p. 408); snout with blunted 

 tip, projecting slightly from the general anterior contour; anterior margins of disc 

 slightly sinuous in large specimens and rather more so in small ones (much as in 

 G. micrura), weakly to moderately convex a little anterior to level of eyes, slightly 

 concave at level of eyes to spiracles, and increasingly convex toward outer corners, the 

 latter moderately rounded or more abruptly so; posterior margins weakly and almost 

 evenly convex or nearly straight, and slightly scalloped, corresponding to the supporting 

 radials; posterior corners broadly rounded and continuous with the strongly convex 

 and short inner margins. Axis of greatest breadth about 58-65 % of distance rearward 

 from tip of snout toward rear limits of disc. Tail from center of cloaca about half 

 (50—52 "/o) ^s long as distance from center of cloaca to snout and a little less than ^4 

 (22—23 °/o) ^s long as width of disc; a low ridge on both upper and lower surfaces of 

 tail extending to tip, the upper ridge from a short distance posterior to rear point of 

 emergence of spine, the lower ridge from about the level of rear corners of pelvics. 



One or two large saw-edged tail spines a little anterior to midpoint of tail, directed 

 rearward and rising only a little above dorsal surface of tail; spines with a median groove 

 above and a wider channel on either side below, much as in the Dasyatidae, except that 

 the spines are wider relative to their length; the lateral teeth strongly recurved, their 

 outer cutting edges arcuate. If there are two tail spines, the larger is the more recently 

 formed in some specimens (as indicated by relative stages in development) but perhaps 

 not in all.^' The spine, on first emerging from the skin, consists of a spear-like point 

 alone, the lateral teeth forming successively as the spine increases in length, the number 

 of teeth increasing from 17—18 on small specimens (450— 550 mm broad) to 28 on 



x8. Distance between eyes 9.3, 9.6. 



19. On a specimen 1,208 mm wide, the two spines are of about equal length (67-68 mm), hence the order in which they 



were produced is not clear. Nor is it clear whether some specimens produce two spines and others only one, or whether 



those with only a single spine have lost one member of the pair. 



