2 74 Memoir Sears Foundation for Marine Research 



center of cloaca to first dorsal fin about 70 "/o as great as distance from center of cloaca 

 to tip of snout, its length to tip nearly as great as distance from center of cloaca to 

 snout in halfgrown specimens, relatively a little less in adults. 



Disc smooth along a narrow marginal band rearward from tip of snout in males 

 to maturity and probably in females as well; rough elsewhere with large prickles or 

 small spines, closest together abreast of eyes, on outer parts of pectorals, and over 

 rump region; sparser between orbits and outward from shoulders; males may develop 

 scattered naked areas at maturity on central parts of pectorals; tail thickly and 

 uniformly prickly above, sparsely so along lateral folds; disc without thorns (except for 

 alar spines of males), but tail with a median row of 21— 26 large and conspicuous thorns 

 on strongly striate bases from a little anterior to axils of pectorals to first dorsal fin; 

 also one large thorn in interspace between first and second dorsals; inner parts of pelvics 

 prickly, outer portions smooth; dorsals prickly; caudal membrane smooth or with a few 

 minute prickles. Alar spines of sexually mature males in 3—4 rows. Lower surface of 

 disc smooth, but tail with a narrow prickly band along either margin rearward from 

 axils of pelvics. 



Snout anterior to orbits about 3.6 times as long as distance between orbits, its 

 length in front of mouth about 2.5 times as great as distance between exposed nostrils. 

 Orbit a little more than half as long as distance between orbits, and about as long as 

 spiracle. Distance between first gill openings 2.1 times as long as distance between ex- 

 posed nostrils, between fifth gill openings 1.7 times; first gill openings 1.2 times as 

 long as fifth and about 1 7 "/o as long as breadth of mouth. Nasal curtain fringed with 

 about 10 short rounded lobelets; expanded posterior (outer) margin of nostril smooth. 

 Mouth nearly straight in females, a little arched in adult males. 



Teeth l^jf, with sharp thorn-like cusp on rounded base in both sexes, rather loosely 

 spaced in regular transverse series, much as in R. hyperborea and R. lintea. 



First and second dorsals about equal in size, brush-shaped, with jagged posterior 

 margin on specimen seen. Interspace between dorsals a little less than half as long as 

 base of first dorsal. Caudal membrane beyond second dorsal a little shorter than base 

 of first dorsal. Pelvics deeply concave outwardly; anterior margin about 50 "/o as long 

 as distance from its own origin to rear tip of pelvic; anterior lobe broadly rounded at 

 tip and strongly scalloped along posterior edge, thus marking the positions of radial 

 cartilages ; posterior lobe with moderately convex and somewhat wavy outer margin, the 

 rear tips subangular, reaching back about Vs of the way from axils of pelvics toward 

 first dorsal. 



Anterior rays of pectorals extending forward about 85 % of distance from level 

 of fronts of orbits toward tip of snout. 



Color. Upper surface uniformly pale brown or bluish gray without dark markings, 

 paler or whitish around posterior edges of pectorals ; lateral folds on tail either of same 

 color as upper surface or white. Lower surface of disc white with small sooty blotches 

 irregularly distributed around margins of pectorals; pelvics white below, sometimes with 

 sooty margins ; lower surface of tail white anteriorly but pale brown rearward from a 



