244 Memoir Sears Foundation for Marine Research 



tip of snout, then weakly" convex rearward in small specimens, weakly concave opposite 

 spiracles in partly grown of both sexes and in adult females, and a little more deeply 

 so in adult males; outer and posterior corners broadly rounded, posterior margins gently 

 convex. Axis of greatest breadth on adult males about 75 "/o of distance back from snout 

 toward axes of pectorals, about 70 '/o on adult females. Tail with narrow lateral folds 

 beginning posterior to axils of pelvics by a distance equal to about twice diameter of eye 

 and extending to extreme tip; its length from center of cloaca to origin of first dorsal 

 about 80 »/o as great as distance from center of cloaca to tip of snout on small and 

 medium-sized specimens, about 70 "/o on large; extreme length of tail from center of 

 cloaca about i. 0-1.2 times as great as distance from cloaca to snout. 



Young specimens with 3-4 thorns on each shoulder and with others between orbits, 

 surrounding eyes, and along margins of rostral ridge to tip of snout; a row of 12-16 

 thorns, about uniform in size, along midline of disc from nuchal region; 16-18 on tail 

 to first dorsal fin, this row flanked by a second less regular row of slightly smaller thorns 

 from close behind pectoral girdle and by a third irregular row of smaller thorns low down 

 on either side of midsector of tail. Outer anterior parts of pectorals loosely strewn with 

 small thorns, but posterior corners and considerable areas along either side of mid-dorsal 

 ridge bare. 



With growth, the thorns of the mid-dorsal row are lost from both the disc and tail,'* 

 and those between the orbits decrease in number and relative size, while the bare areas 

 expand over the inner parts of the pectorals and abreast of the spiracles, eyes, and rostral 

 ridge; however, the thorns on the shoulders increase in number and a thorny area 

 develops on the central part of the posterior lobe of each pelvic. 



Specimens that are V2-V3 grown have a patch of thorns on the tip of the snout, a 

 regular or irregular series on each edge of the rostral ridge, a patch of small thorns in 

 front of the orbit, a row around its inner margin, several larger ones (one usually notice- 

 ably larger) just behind the orbit, and a few small ones between the orbits. The pectorals 

 are rough with small thorns and prickles along the anterior margins nearly to the poste- 

 rior corners, with larger thorns scattered abreast of the spiracles and eyes and on the 

 posterior parts. Each shoulder bears a roughly triangular patch of medium-sized thorns 

 (variable in number), the outermost 2-3 usually considerably largest; also, there are 2-3 

 irregular rows of medium-sized thorns with radiate bases along either side of the mid- 

 dorsal line from the pectoral girdle rearward past the first dorsal fin,'« these thorns de- 

 creasing in size and in regularity rearward, not much larger in any one of these rows than 

 in the other rows, and those lowest down on the sides of the tail smallest. The central 

 parts of the posterior lobes of the pelvics are prickly at first but later become thorny. 

 The first and second dorsals are prickly. Otherwise the skin is smooth, with extensive 

 bare areas along either side of the mid-dorsal zone, alongside the spiracles and eyes, and 

 between the rostral ridge and the anterior radial cartilages of the pectorals. 



75. Twenty inches is the greatest length at which a definite midrow of thorns still persists in any specimen that we 

 have seen; they are usually lost by the time specimens are half-grown. 



76. Sometimes four rows locally on one side of the tail or the other. 



