Fishes of the Western North Atlantic 455 



rior corners, merging insensibly into moderately convex inner margins. Trunk opposite 

 spiracles about i. 0—1.2 times as deep as distance between spiracles and at level of pec- 

 toral girdle about i.i — 1.4 times as deep (thus much deeper than in the dasyatids or 

 Butterfly Rays); progressively thinner posteriorly and outwardly. Tail, from center of 

 cloaca, up to a little more than 3.5 times as long as body from cloaca to tip of snout 

 when intact in small specimens ;*' perhaps somewhat shorter relatively in larger individ- 

 uals; more or less of its terminal part often lost; ovoid in cross section as far rearward 

 as tail spines, rounded and extremely slender thence rearward to tip; upper and lower 

 surfaces of tail each with a low longitudinal ridge originating close behind point of 

 emergence of free portion of tail spine (or most posterior member of the group of 

 spines if there are two or more) and distinguishable rearward for a distance somewhat 

 more than twice as long as distance from axils of pelvics to spine. 



Tail spines 1—3 in specimens seen, 4—5 reported, perhaps most commonly two,** 

 similar in cross section to those of the dasyatid Sting Rays, with spear-like tip, recurved 

 lateral teeth, and forked root; origin of spine (or of first spine if there be two or more) 

 close behind rear tip of dorsal fin; free portion of the longest spine seen about half as 

 long as distance between spiracles or nearly as long as distance from its origin to root 

 of tail at axils of pectorals. 



Skin apart from tail spines perfectly smooth. 



Head anterior to spiracles projecting conspicuously from general outline, high- 

 arched, its dorsal surface sloping abruptly downward in rounded contour a little anterior 

 to eyes; its upper surface with a broad shallow median furrow from level of front of 

 eyes to level of posterior ends of spiracles; sides of head anterior to spiracles nearly 

 flat or weakly convex, somewhat converging downward ; lower surface of head weakly 

 convex transversely. Orbits only moderately prominent ; eyes circular, their upper mar- 

 gins about at point of transition between sides and dorsal surface of head; their diameter 

 about 40—45 7o as long as distance between eyes and 80 "/o as long as greatest length 

 of spiracles. Spiracles close behind eyes but at a higher level, encroaching on upper 

 surface of head, wide open in all specimens examined, their length a little less than half 

 as great as shortest distance between them; their margin smooth, without trace of any 

 spiracular appendage. Anterior outlines of gill openings weakly sinuous, the second and 

 third (longest) about as long as diameter of eye or about half the diameter of orbit; 

 fifth only about ^/j that long; distance between inner ends of first pair about 3.5 times 

 as great as distance between exposed nostrils; distance between inner ends of fifth gills 

 about 65—68 "/o as great as distance between first gills. Nostrils extending forward about 

 to level of front of cranium, connected posteriorly with mouth by a broad shallow groove; 

 floor of nasal groove and posterior margin of internarial septum set with low rounded 

 knobs; nasal curtain indented in midline by a deep notch, its outer corners widely ex- 



61. Relatively longer in embryos; see Developmental Stages, p. 459. 



62. Among 24 specimens from Beaufort, North Carolina, and Key West, Florida, four had one spine, nine had two 

 spines, four had three, five had four, and two had five spines (Gudger, Bull. Hist. Med., ij^, '943: 481). One with 

 five spines was pictured by Quoy and Gaimard (Voy. 'Uranie,' Zool., 1S24: 200, pi. 43, fig- 3), and another has 

 been reported to us from Key West, Florida, by Lt. Comm. C. Saunder?, U. S. N. R. 



