448 Memoir Sears Foundation for Marine Research 



Dorsal fin: vertical height 2.1, 2.1 ; length of base 4.4, 4.3. 

 Pelvics: outer margin 12.8, 13.7. 



Distance: from tip of snout to center of cloaca 55.2, 60.3; from center of cloaca 

 to origin of tail spine 17.6, 22.2; to tip of tail 87.0, — . 



Disc 1.5— 1.7 times as wide as long from tip of subrostral fin to level of posterior 

 corners of pectorals; anterior margins weakly convex; posterior margins moderately 

 concave, increasingly so outward; outer corners moderately rounded (a little more 

 broadly so than in M. freminvillit); posterior corners about a right angle, blunted at tip; 

 inner margins moderately convex (Fig. 104), about as long as breadth of mouth. Axis 

 of greatest breadth about ^j^ of distance rearward from tip of subrostral fin toward axils 

 of pectorals; breadth between axils of pectorals about as great as distance between outer 

 ends of first pair of gill openings on large specimens and about as great as distance be- 

 tween inner ends of first gills on small ones; thickness of disc at pectoral girdle a little 

 less (85—93 "/o) than distance between spiracles. Tail moderately stout anterior to dorsal 

 fin and spine, tapering thence rearward to whiplash tip, its length from center of cloaca 

 a little more than twice as great as distance from tip of snout to center of cloaca in smallest 

 specimens, probably about as long as in M.freminvillii in larger ones.^* 



One tail spine on specimens seen (probably sometimes two); its origin close behind 

 rear end of base of dorsal and posterior to axils of pelvics by a distance a little more than 

 1.5 times as great as distance between eyes; about as long as distance between eyes 

 or a little longer when fully developed; about i/, as broad as long at base where exposed; 

 its lateral teeth much as in M.freminvillii. 



Skin apart from tail spine perfectly smooth on females; conditions on male not 

 known. 



Upper surface of crown weakly concave longitudinally from forehead to level of 

 spiracles, as in M.freminvillii. Orbits not prominent, about 40-60 */o ^s long as distance 

 between orbits. Spiracle much as in M.freminvillii., its length about 1.1-1.9 times as 

 great as that of orbit. Gill openings sinuous, as in M. freminvillii, first to third about 

 0.5-0.8 times as long as orbit; distance between inner ends of first pair 2.8—3.1 times 

 as great as distance between exposed nostrils; distance between inner ends of fifth gills 

 about 56—62 "/o as great as that between first gills. Free margin of joint nasal curtain 

 straight or weakly concave, irregularly fringed with short lobelets, single, bifid or trifid 

 at tips. Mouth weakly arched, occupying about half of breadth of head. Floor of mouth 

 posterior to dental plate with 5—6 short fleshy papillae; transverse curtain on roof of 

 mouth with fringed edge. 



Teeth similar in the two jaws; normally y, but occasionally yfrom interpolation of 

 an extra series on one side or the other ;^* those of median series about four times as 

 broad (transversely) as long (anteroposterlorly) and about four times as broad as those of 

 lateral series; their length (anteroposterlorly) about Ve— V4 ^^ great as diameter of eye; 



43. Maximum length about 1.8 times as great as length of disc in larger specimens seen, but tip evidently lost. 



44. Eight rows in the upper jaw, seven in the lower jaw, in one specimen in our Study Material; seven in both jaws 

 in all others. 



