290 Memoir Sears Foundation for Marine Research 



Distinctive Characters. B. colesi is marked off from all other known members of its 

 genus in the western Atlantic by a tail that is at least no longer from the axils of the 

 pelvics to the origin of the second dorsal than from the axils of the pelvics to the tip 

 of the snout, by the fact that the midzone of the disc between the pectoral and pelvic 

 girdles bears only one or two conspicuous thorns, if any, and by the dark markings on 

 its upper surface. The shortness of its rostral cartilage separates it from the hard-nosed 

 Skates of the genus Raja. 



Description. Proportional dimensions in per cent of total length. Male, 294 mm 

 (Harv. Mus. Comp. Zool., No. 36497), female, 333 mm (Harv. Mus. Comp. Zool., 

 type, No. 36374), from Cuba. 



Disc: extreme breadth 49.3, 48.0; length 41.5, 45.9. 



Snout length: in front of orbits 8.3, 9.8; in front of mouth 8.8, 1 1.2. 



Orbits: horizontal diameter 4.8, 4.5; distance between 2.5, 3.0. 



Spiracles: length 2.9, 2.8; distance between 5.8, 5.7. 



Mouth: breadth 7.1, 6.3. 



Nostrils: distance between inner ends 6.^^ 6.6. 



Gill openings : lengths, ist 1.4, 1.8; 3rd 1.4, 1.8; 5th 1.3, 1.5; distance between 

 inner ends, ist 12.2, 13.6; 5th 5.8, 6.6. 



First dorsal fin: vertical height 1.4, 1.5; length of base 4.8, 3.6. 



Second dorsal fin: vertical height i.o, 1.5; length of base 4.1, ^t-^)- 



Pelvics: anterior margin 10.5, 10.2. 



Distance: from tip of snout to center of cloaca 38.4, 41.4; from center of cloaca 

 to 1st dorsal 51.0, 50.0; to tip of tail 61.6, 58.6; from rear end of 2nd 

 dorsal base to tip of caudal 1.4, 1.5. 



Interspace between: ist and 2nd dorsals 0.3, 0.0. 



Disc about i. 0—1.2 times as broad as long, very obtuse in front; tip of snout 

 marked by a small rounded prominence; maximum anterior angle in front of spiracles 

 about 135°; anterior margins moderately and evenly convex on young and on females 

 to maturity but weakly concave opposite and posterior to spiracles on adult males; 

 outer corners well rounded, more broadly so on adult males than on females; posterior 

 corners broadly rounded, merging into convex inner margins. Axis of greatest breadth 

 about 70 "/o of distance back from tip of snout toward axils of pectorals. Tail with 

 narrow lateral folds for entire length from a little behind tips of pelvics, widening 

 posteriorly; its length from center of cloaca to origin of first dorsal about 1.2 — 1.3 times 

 as great as distance from center of cloaca to snout, about 1.3— 1.5 times as great to 

 origin of second dorsal, and about 1.4— 1.6 times as great to tip. 



Disc rough with small prickles on adults of both sexes except close along anterior 

 and posterior edges; a narrow band of thorns along anterior margins from level of 

 spiracles forward, very small on females, larger on adult males ; a cluster of small thorns 

 on rostral ridge about halfway between level of fronts of orbits and tip of snout; lo-i i 

 thorns around inner margin of orbit, the row interrupted midway; two thorns inward 



