268 Memoir Sears Foundation for Marine Research 



around inner margin of orbit; one on each shoulder; a row of thorns along midline of 

 back, lo— 12 large ones anterior to axils of pelvics, followed by successively smaller ones 

 along tail until no longer distinguishable from the prickles a short distance anterior to 

 first dorsal. Large specimens of both sexes with 2—3 preocular thorns, 1-2 postoculars, 

 about eight along inner margin of orbit, 3—5 on each shoulder, and 16 or more larger 

 and smaller thorns spaced irregularly along midline of disc; tail usually with 20—30 

 thorns in midrow along anterior one-half to two-thirds, these of different sizes, progres- 

 sively smaller rearward; each side of tail low down with 1—3 irregular rows of thorns 

 along anterior part, grading down to minute prickles above, below, and rearward; pos- 

 terior one-third to one-half of tail without large thorns — the most distinctive character 

 of the species. Females remain prickly on the upper surface as a whole to maturity (in 

 addition to thorns), densely so on the tail, but irregular bare areas develop in the general 

 region of the shoulders and around the outer parts of the pelvics. Maturing males lose 

 the prickles from the central portion of the disc as a whole, but they develop a few 

 medium-sized thorns on the anterior part of the rostral ridge; also smaller thorns over 

 the anterior parts of the pectorals (only prickly in females) and large thorns over a roughly 

 triangular area on either side abreast of the eye and anterior to it. Alar spines of mature 

 males in two rows on either side, 13—14 in each row. Lower surface of disc smooth in 

 small specimens, but prickles develop later along a narrow marginal band from snout 

 back about halfway toward level of nostrils; lower surface of tail either densely prickly 

 throughout on young of both sexes and on females to maturity, or at most with a narrow 

 naked median band, but becoming generally smooth in males by maturity. 



Snout in front of orbits about 3.1—4.0 times as long as distance between orbits, 

 its length in front of mouth about 1.8— 2.1 times as long as distance between exposed 

 nostrils. Orbit about 1.5 times as long as spiracle. Distance between first gill openings 

 1.9 times as long as distance between exposed nostrils, 0.9—1.0 times between fifth 

 gill openings; first gill openings 1.4— 1.6 times as long as fifth and about 26 % as 

 long as breadth of mouth. Nasal curtain as well as expanded posterior (outer) margin 

 of nostril fringed. Mouth moderately arched in adult females, more strongly so in 

 adult males. 



Teeth ||Ez|g) evenly rounded in anterior rows but with faintly indicated cusps in 

 posterior rows and closely crowded in quincunx in young specimens and in females to 

 maturity; but teeth of mature males with high, recurved, sharp-pointed cusp and spaced 

 more loosely in transverse series. 



First and second dorsals similar in size and shape, confluent at base. Caudal mem- 

 brane posterior to base of second dorsal about half as long as base of first dorsal. Pelvics 

 deeply concave outwardly and strongly scalloped around the indentation ; anterior margin 

 about 75—85 "/o as long as distance from its own origin to rear tip of pelvic in half-grown 

 and large specimens, as much as 90 "/o in young; anterior lobe narrow, including only 

 two radial cartilages besides the first and stoutest; posterior lobe with moderately convex 

 outer margin and well rounded posterior corner. Claspers of mature male extend back 

 about 1/2 to '/5 the distance from axils of pelvics toward first dorsal. 



