Fishes of the JVester'n Northr Atlantic 169 



to 1st dorsal 37.0, 32.3; to tip of tail 52.2, 48.5; from rear end of 2nd 

 dorsal base to tip of caudal 2.0, 2.8. 

 Interspace between: ist and 2nd dorsals 0.9, 1.6. 



Disc about 1.2 — 1.3 times as broad as long; anterior contour about a right angle, 

 a little more obtuse in southern specimens than in northern;*' anterior margins weakly 

 concave posterior to snout, weakly convex abreast of spiracles in females and only 

 slightly more so in adult males; posterior corners broadly rounded, the outer corners 

 more narrowly so. Axis of greatest breadth 73-76 "/o of distance back from tip of 

 snout toward axils of pectorals. Tail with moderately wide lateral folds, its length from 

 center of cloaca to origin of first dorsal about 0.7—0.8 as great, and from center of 

 cloaca to origin of second dorsal about 0.8-0.9 ^s great, as distance from center of 

 cloaca to tip of snout, on both large and small specimens. 



Upper surface of disc with 1—5 thorns on each shoulder region;*' 2-4 thorns 

 at inner end of spiracle; 3-4 close behind orbit and as many close in front of it; also 

 an irregular row around inner margin of orbit; a single continuous midrow, extending 

 rearward along disc from nuchal region, the thorns varying in size from place to place 

 (perhaps with age) and increasing in number with growth from 14-16 in small speci- 

 mens (185—267 mm long) to 33—39 in those longer than 400 mm. 



On southern specimens (Figs. t,i,, 34)/* in addition to thorns, the upper surface 

 of the disc, the base of the tail, and the central part of the pelvics is generally beset with 

 small prickles from the time of hatching; females either continue so until maturity or 

 may develop small naked areas outward and rearward from the shoulders. But mature 

 males continue to be prickly only on the outer anterior parts of the pectorals, on the 

 head outward from the eyes, in front of the eyes, and between the orbits. Northern 

 examples*" seem less rough; the upper surface of the disc and the pelvics is naked at 

 hatching (Fig. 35) except for the characteristic thorns; later the females become prickly 

 along the margins of the disc rearward from the level of the orbits (perhaps more gener- 

 ally so over pectorals in some cases), in a band along either side of the mid-dorsal ridge 

 from the nuchal region rearward, over a patch in front of each orbit, along the edges 

 of the rostral ridge, on the tip of the snout, and sometimes in the space between the 

 orbits (Fig. 32). Mature northern males are prickly only along the anterior margins 

 of the pectorals posterior to the level of the spiracles, over patches in front of the eyes, 

 on the rostral ridge and tip of snout, and hence they are considerably smoother than 

 adult females. 



The tail, from the axils of the pectorals to the first dorsal, has a median row of 

 about 16-19 moderately large thorns on newborn specimens which increase to 26—32 



S6. Maximum anterior angle in front of spiracles 90° in two specimens from Woods Hole; 100-105^ in two from North 



Carolina and 92-105° in three from South Carolina. 

 87. One or two on large specimens of both sexes from Buzzards Bay, Massachusetts and on a female from Charleston, 



South Carolina; 3-5 on a smaller but sexually mature male from the latter locality. Sometimes these thorns are 



lacking. 

 XS. Florida and South Carolina. 89. Woods Hole, Massachusetts. 



