42 2 Memoir Sears Foundation for Marine Research 



rear limits of disc. Tail from center of cloaca about as long as distance from center of 

 cloaca to tip of snout, or a little shorter; its basal portion, anterior to spine, tapering 

 gently and flattened moderately dorsoventrally, each side with a low but definitely 

 marked dermal ridge or keel. 



Tail spine about as long as snout in front of orbits, or about half as long as distance 

 from its origin to center of cloaca; its origin a little posterior to midlength of tail from 

 center of cloaca; spine with about 20-25 recurved and sharp lateral teeth toward tip 

 but smooth-edged along basal ^/s to V4 of its length; only one spine on specimens 

 examined, but sometimes two.** 



Skin, apart from tail spine, naked in embryos ; but midbelt of back, from nuchal 

 region rearward, roughened from soon after birth by low blunt tubercles, sparsely 

 scattered finally in three or four irregular rows on disc and in four or five rows on tail 

 rearward to spine; those along tail somewhat the largest in some cases; a series of 

 rather stronger recurved thorns also developing close along dorsal margin of caudal fin 

 on either side; large specimens with mid-dorsal tubercles extending forward to level of 

 posterior parts of orbits and to zone between eyes, or even a little farther in some; 

 thorny belt finally expanding laterally to cover an irregular area over each shoulder. 

 But naked patches sometimes develop on the posterior part of the disc as maturity is 

 approached, perhaps more often on females than on males.*' Lower surfaces of both 

 disc and tail naked. 



Snout in front of orbits about as long as distance between outer margins of orbits, 

 its length in front of mouth about 1.9—2.2 times as great as distance between exposed 

 nostrils and 0.8—1.0 times as great as distance between inner ends of first gill openings. 

 Orbit about as long as distance between orbits. Spiracle close behind orbit, about 

 0.7—0.8 times as long as orbit, its inner margin with a low knob reminiscent of the 

 embryonic spiracular lobe (described under Developmental Stages, p. 425). Distance 

 between inner ends of first gill openings 2.2—2.3 times as great as distance between 

 exposed nostrils; distance between inner ends of fifth pair about 73-75 % ^s long as 

 distance between first pair. Nasal curtain reaching to mouth, its margin weakly and 

 evenly arcuate, fringed with a close-set series of short lobes with secondarily fringed 

 margins (Fig. looA). Mouth nearly straight. Floor of mouth with 3-5 papillae. 



Teeth |^|q (two specimens); those of young of both sexes and of females to matu- 

 rity close-set in quincunx; low and narrow-oval, their long axes parallel with jaw; the 

 functional surface with deep furrow from side to side, and somewhat irregular in out- 

 line; teeth of sexually mature males somewhat more loosely spaced, with high conical 

 cusp, slightly blunted at tip; about 4-6 rows in upper jaw and 7-9 rows in lower in 

 function simultaneously. 



Caudal fin broadly rounded at tip, with weakly convex upper and lower margins, 

 about equally wide above axis as below, its greatest breadth about ^l^—^U as great as 

 its length along ventral margin; its ventral origin under or a little posterior to origin 



98. Duerden, J. Inst. Jamaica, 2, 1895: 166; Fowler, Rep. N. J. Mus. (1906), 1907: pi. 78. 



99. There appears to be no definite sexual contrast in this respect. 



