I 8o Memoir Sears Foundation for Marine Research 



convex; inner margins convex to axils. Axis of greatest breadtli about 70—72 "/o of 

 distance back from tip of snout toward axils of pectorals. Tail with narrow lateral 

 folds low down along posterior two-thirds, its length from center of cloaca to origin 

 of first dorsal about i.i times as great as distance from center of cloaca to tip of snout 

 in newly hatched specimen, decreasing relatively to about 0.85-0.95 that great in 

 adults; distance from center of cloaca to tip of tail 1.2 -1.3 5 times as great as distance 

 from cloaca to snout after embryonic prolongation is lost (4 specimens, 441-452 mm 

 long)."9 



On newly hatched specimens, upper surface conspicuously rough; inner and an- 

 terior parts of pectorals closely set with thorns, the largest posteriorly; 6—10 thorns 

 on each shoulder region; 2-3 behind each eye, with two or more in front of it; 2-3 

 along inner margin of orbits, and a few in space between orbits; a row along either 

 edge of rostral cartilage, with a group of thorns of various sizes on tip of snout; also a 

 regular mid-dorsal row of about 5 or 6 thorns on disc rearward from pectoral girdle and 

 15—17 on tail, flanked by a lateral row on either side extending equally far rearward; 

 another less regular row lower down along anterior half of tail. With growth the thorns 

 increase in number to: 2—4 irregular rows along either side of midline of disc and of 

 anterior part of tail; 1—2 rows near tip of tail; an irregular triangular group of about 

 30-60 covering nuchal and shoulder region; 3—8 behind eye and 8—15 in front 

 of it; 9—12 along inner margin of orbit and several between orbits; and an irregular 

 double row along each edge of rostral cartilage, with a cluster at tip of snout. On the 

 other hand, some of the large thorns are lost progressively from the inner parts of 

 the pectorals, their anterior margins continuing rough with large thorns. Specimens 

 from the Gulf of Maine and southward also lose the median row of thorns posterior 

 to the nuchal region by the time a length of 300—350 mm is reached, but mature 

 individuals (to at least 469 mm) that we have seen from the lower St. Lawrence River 

 still bear this median row of thorns. Skin of disc and tail smooth between thorns in all 

 specimens examined. Both dorsals prickly posteriorly in small specimens and prickly 

 toward margins on larger. Pelvics prickly on small specimens; naked or with only a 

 few small thorns on larger males and on partly grown females, but with a thorny 

 area developing on mature females. 



At sexual maturity the outer posterior parts of the pectorals become increasingly 

 thorny in females, but maturing males lose most of the thorns from the inner parts 

 of their pectorals and some from the mid-dorsal ridge, so that they are noticeably 

 smoother than mature females, but there is wide variation from specimen to specimen. 

 Alar spines of mature males in 2—3 rows on outer two-thirds of pectoral; 13-14 

 spines in each of inner two rows, 5—7 in third row. 



Lower surface wholly naked in newly hatched specimens, but snout soon becoming 

 prickly, the rough area expanding as a narrow band along margin of disc about to level 

 of nostrils in half-grown specimens, about to level of mouth in adults. 



119. In three specimens, 346-469 mm long, from the St. Lawrence River, the distance from cloaca to tip of tail was 

 only 0.93-1. 18 as great as the distance from snout to cloaca. 



