296 Memoir Sears Foundation for Marine Research 



margins both strongly convex. Axis of greatest breadth about 75 "/o of distance back 

 from snout toward axils of pectorals. Tail slender, its lateral folds narrow, confined 

 to posterior two-thirds, broadening a little rearward; its length from center of cloaca 

 to first dorsal about 1.3— 1.4 times as great as distance from center of cloaca to snout, 

 about 1.6— 1.8 times as great to tip. 



Upper surface of disc (except for tip of snout) and tail rough with small prickles 

 on half-grown specimens and on females to maturity, but mature males smoother along 

 a narrow marginal band and over areas of varying extent on inner parts of pectorals; 

 both sexes with 9—15 small thorns around inner margin of orbit, the series sometimes 

 interrupted midway; 1—2 small thorns inward from inner end of spiracle, and 1—2 on 

 each shoulder close to midline; also a median row of 50—100 or more thorns of various 

 sizes grading down to prickles from nuchal region to first dorsal fin, the row con- 

 tinuous on some specimens but more or less interrupted on others between pectoral 

 and pelvic girdles and much more prominent on some than on others; tail posterior to 

 axils of pelvics with 1—2 additional rows of small thorns or large prickles along either 

 side; anterior parts of dorsals and interspace between first and second dorsals prickly; 

 pelvics either smooth or more or less prickly along inner parts. Sexually mature males 

 with a patch of small thorns on outer part of disc opposite orbits, their alar spines in 

 2—4 rows opposite outer corners of pectorals, 3—6 spines in each row. Lower surface 

 smooth. 



Snout in front of orbits 1.6— 2.1 times as long as orbit, its length in front of mouth 

 2.1—2.6 times as great as distance between exposed nostrils. Orbit about 1.5 times as 

 long as distance between orbits and about two times as long as spiracle. Distance 

 between first gill openings 2.1—2.7 times as long as distance between exposed nostrils, 

 1.3— 1.6 times between fifth gill openings; first gill openings i.i— 1.3 times as long as 

 fifth and about 18—26 "/o ^s long as breadth of mouth. Nasal curtain and posterior 

 (outer) margin of nostril both smooth-edged. Mouth weakly arched centrally. 



Teeth jgZ^g; close-set in quincunx, with obscure transverse cutting edge and 

 faintly indicated cusp in young and in females to maturity, but with long and sharp 

 recurved cusp in mature males. 



Dorsals similar in shape, the base of the first equal to or slightly longer than that 

 of the second, usually separated by an interspace 0.25—1.0 times as long as base of first 

 dorsal but sometimes confluent. Caudal membrane posterior to second dorsal about half 

 as long as base of second dorsal. Pelvics deeply concave outwardly in subtriangular con- 

 tour, scalloped around the indentation; anterior margin about 90— 100 "/o as long as 

 distance from its own origin to rear tip of pelvic; anterior lobe slender, tapering to a 

 narrowly-pointed tip, of two slender radials in addition to the first stout one; posterior 

 lobe with moderately convex and more or less wavy outer margin, extending nearly 1/4 

 the distance rearward from level of axils of pectorals toward first dorsal fin, the rear 

 tip narrowly rounded on young of both sexes and on adult females but more pointed 

 on adult males. Claspers of sexually mature males slender, reaching about Va the distance 

 from axils of pelvics toward first dorsal, their tips simple. 



