Fishes of the Western North Atlantic 257 



terior margins slightly concave close behind tip of snout, weakly and evenly convex 

 thence rearward to outer corner of pectorals on newly-hatched specimens but becom- 

 ing weakly concave with growth at level of eyes and spiracles and about equally so in 

 both sexes to maturity ji"' posterior corners much more broadly rounded than outer 

 corners. Axis of greatest breadth about 70 % of distance back from snout toward axils 

 of pectorals. Tail with narrow lateral folds low down and beginning close behind axils 

 of pelvics; its length from center of cloaca to origin of first dorsal about 80 "/o as great 

 as distance from center of cloaca to snout in young, 60-70 "/o at maturity; extreme 

 length of tail from center of cloaca about i.i — 1.2 times as great as distance from cloaca 

 to snout in young, but about 0.9— i.i times in half-grown specimens and adults. 



Upper surface with a median row of i i — 19 large conspicuous thorns on radiate 

 bases from nuchal region back nearly to first dorsal fin, usually 1-2 more on adults 

 than on young specimens ;!"* 6-9 of these anterior to axils of pectorals and about an equal 

 number along tail, the thorn nearest to the first dorsal sometimes very small ; midbelt 

 of back with 1—3 irregular rows of smaller thorns on either side of the midrow, these 

 confined to disc on very small specimens but extending along tail to first dorsal fin 

 on adults, decreasing in size rearward; anterior and median parts of pectorals with 

 scattered thorns, most closely spaced from level of spiracles forward; 2-6 near tip of 

 snout, sometimes one pair conspicuously largest; one prominent thorn close in front of 

 eye, one on inner posterior margin of orbit, and one close to inner end of spiracle; 

 also 2—3 on each shoulder, the most posterior of these usually largest; skin of disc 

 usually without prickles around eyes, behind spiracles, behind shoulders, and on outer 

 posterior parts of pectorals. Skin also without prickles elsewhere between the larger 

 thorns on some specimens but more or less prickly on others, especially on the snout, 

 between the orbits and on the shoulders; skin above eyes either naked or prickly; 

 tail with a thick-set belt of very small prickles low down along either side from axils 

 of pectorals to below dorsals, these prickles being especially conspicuous on small 

 specimens; dorsals prickly; space between dorsals with one small thorn, or none, if the 

 fins are separated; caudal membrane sometimes with a few minute prickles, but usually 

 smooth; pelvics sometimes naked, but more often with central area more or less prickly, 

 sometimes with 1—2 thorns. Sexually maturing females become increasingly thorny 

 over the midzone of the disc in general, on the shoulders, and over the outer anterior 

 parts of the pectorals ; they also become increasingly prickly between the thorns. But 

 maturing males lose most of the thorns from the pectorals except along the anterior 

 margins. Alar spines of mature males in 'i^—^ rows, each row about as long as distance 

 between outer margins of orbits. Lower surface smooth on small specimens, but prickles 

 usually develop with growth on the midzone of the snout about halfway back toward 

 the mouth, along the extreme outer margins of the disc to the level of the spiracles in 



107. We have a male 540 mm long with well developed claspers, caught oft" South Carolina, on which the anterior margin 

 of disc is sharply indented opposite level of spiracles. 



loS. From the Gulf of Maine, three out of five small specimens, 126-153 mm long, had 12 mid-dorsal thorns, one had 

 13, and one had 14; among 31 larger specimens, one had 11, two had 12, eleven had 13, nine had 14, four had 15, 

 and four had 16; West Greenland specimens had 13-19 (Jensen, Spol. Zool. Mus. Hauniensis, 9, 1948: 28). 



