2 2 o Memoir Sears Foundation for Marine Research 



and in many cases the upper surface of each pectoral is marked with a large and con- 

 spicuous ocellar spot. 



Description. Proportional dimensions in per cent of total length. Male, 1,064 mm, 

 and female, 1,187 "^"^> from off Massachusetts (Harv. Mus. Comp. Zool., No. 368). 

 Disc: extreme breadth 74.3, 72.0; length 53,9, 51.8. 

 Snout length: in front of orbits 15.2, 15.7; in front of mouth 16.8, 15.6. 

 Orbits: horizontal diameter 3.8, 2-S'-< distance between 5.4, 5.5. 

 Spiracles: length 3.0, 2.5; distance between 7.2, 7.0. 

 Mouth: breadth 9.8, 9.2. 



Nostrils: distance between inner ends 8.8, 8.0. 

 Gill openings: lengths, ist 1.8, 2.0; 3rd 2.1, 2.1 ; 5th 1.5, 1.4; distance between 



inner ends, ist 16.5, 17.0; 5th 10.4, 11.4. 

 First dorsal fin: vertical height 3.1, 3.4; length of base 5.7, 6.0. 

 Second dorsal fin: vertical height 2.4, 2.9; length of base 6.1, 4.9. 

 Pelvics: anterior margin lo.o, 10. i. 



Distance: from tip of snout to center of cloaca 51.9, 50.8 ; from center of cloaca 

 to 1st dorsal 31.7, 33-8; to tip of tail 48.1, 49.2; from rear end of 2nd 

 dorsal base to tip of tail 3.8, 2.8. 

 Interspace between: ist and 2nd dorsals 0.8, 1.8. 



Disc about i .4 times as broad as long, the maximum anterior angle in front of 

 spiracles about 82-90°, a little more acute on newborn specimens than on larger; 

 anterior margins weakly concave just posterior to tip of snout, weakly convex opposite 

 eyes and spiracles (no more so in males than in females), weakly concave thence rear- 

 ward; outer corners narrowly rounded, posterior corners more broadly so, posterior 

 margins nearly straight forward but gently convex rearward. Axis of greatest breadth 

 about 70 o/o of distance back from tip of snout toward axils of pectorals. Tail with 

 lateral folds beginning posterior to axils of pelvics by a distance about ^s as long as 

 eye and extending nearly to tip; its length from center of cloaca to origin of first 

 dorsal fin about 76 "/o as great as distance from center of cloaca to tip of snout in 

 newly hatched specimens, about 70 "/o on half-grown ones, and about 66-68 "/o on 

 large; total length of tail about 1.3 times as great as distance from center of cloaca to 

 tip of snout at hatching, decreasing relatively to about as long as body sector, or a 

 little shorter, at maturity. 



Newly hatched specimens with 1-2 thorns in front of orbit and one behind, a 

 row of about 14-17 along midline of tail from a little posterior to axils of pectorals to 

 first dorsal fin, and one in interspace between first and second dorsals; otherwise smooth 

 both above and below. Larger specimens with the pre- and post-ocular thorns replaced 

 by patches of much smaller ones; also thorns in mid-dorsal row on tail increasing to 

 23-40 in both sexes, often irregularly spaced, the most anterior one a little behind 

 axils of pectorals in some specimens but a little behind axils of pelvics in others; an 

 additional continuous row of equally large thorns developing (irregularly at first) low 



