5 04 Memoir Sears Foundation for Marine Research 



distinctive an appearance that it could not be confused with any other Atlantic Ray 

 except some other member of its own family. The position of its mouth, extending across 

 the front of its head instead of on the lower surface, sets it apart from both Mobula and 

 Ceratohatis, if the latter be a valid genus. The fact that it has no teeth in the upper jaw 

 distinguishes it from the somewhat problematical genus Indomanta (see discussion, 

 p. 485). 



Description. Proportional dimensions in per cent of extreme breadth. Male, 3,480 

 mm broad, from Bimini, Bahamas (Harv. Mus. Comp. Zool., No. 37006). 



T)i$c: vertical length 44.5. 



Orbits: horizontal diameter 2.4;i3* distance between 24.8. 



Spiracles: length 1.6; distance between 20.8. 



Mouth: breadth 14.9. 



Nostrils: distance between outer ends 14.1. 



Gill openings: lengths, ist 9.8; 2nd 10. i; 3rd 9.8; 4th 8.8; 5th 7.0; distance 

 between inner ends, ist 10.8; 5th 5.1. 



Dorsal fin: vertical height 4.4; length of base ^.T,. 



Pelvics: anterior (outer) margin 6.2. 



Distance: from center of snout to center of cloaca 36.5; from center of cloaca 

 to tip of tail 37.6. 



Disc, exclusive of cephalic fins, about 2.2 times as broad as long on specimens 

 measured; main portions of pectorals originating about opposite spiracles or a little 

 posterior; anterior margins of pectorals weakly concave and then becoming convex out- 

 wardly; posterior margins rather strongly concave; inner margins weakly convex; outer 

 corners falcate, tapering to narrowly blunted tips; rear corners also narrowly rounded. 

 Axis of greatest breadth about 58 "/o of distance rearward from front of midsector of 

 head toward level of axils of pectorals. Maximum thickness of trunk described as being 

 between 20 and 27 "/o as great as breadth of disc in specimen 15 feet wide,!^' but only 

 1 5 "/o as great as breadth of disc on one 2 i feet wide.^*" Tail from center of cloaca at 

 least as long as distance from cloaca to front of head and perhaps considerably longer in 

 undamaged specimens,^*' tapering to slender tip; its height at rear end of dorsal fin 

 between V4-V3 (about 28 %) as great as length of base of dorsal; its sides somewhat 

 flattened, with shallow longitudinal furrow along anterior quarter of its length, its upper 

 surface with a low ridge reaching about equally far back, its lower surface with a similar 

 ridge extending somewhat farther. 



Some specimens are described as having one or two small serrated spines a little 

 posterior to the dorsal fin.i*^ However, the tails of other specimens (including those 



138. The eye is 1.6. 139. Gunther, Cat. Fish. Brit. Mus., 8, 1870: 498. 



140. Measurements contributed by Fred Huber. 



141. The specimens seen by us have lost part of the end of the tail, as had most of those that have been described pre- 

 viously. 



142. See Lesueur (J. Acad. nat. Sci. Philad., 4, 1824: 117, pi. 6) for account of a 15-16 foot female from off Delaware 

 Bay with one tail spine and of an embryo i foot 1 1 inches wide which was taken from her and which also had one 



