470 Memoir Sears Foundation for Marine Research 



Mouth: breadth 8.7, 7.8. 



Exposed nostrils: distance between inner ends 7.0, 7.1. 



Gill openings: lengths, ist 2.4, 2.2; 3rd 2.7, 2.3; 5th 1.9, 1.9; distance between 



inner ends, ist 16.6, 15.2; 5th 10.9, 10.6. 

 Dorsal fin: vertical height 4.2, 4.8; length of base 5.9, 6.0. 

 Pelvics: outer margin 9.8, 10.9. 

 Distance: from tip of snout to center of cloaca 47.1, 47-4; from center of cloaca 



to origin of caudal spine lo.o, lo.i. 



Disc from forehead to level of rear corners of pectorals about 1.7 times as broad 

 as long, the anterior margins nearly straight near head, changing to weakly convex 

 toward outer corners; posterior margins rather deeply concave outwardly; outer and 

 posterior corners narrowly rounded; inner margins weakly convex; main portions of 

 pectorals arising from sides of head close behind eyes, a little below level of latter. Axis 

 of greatest breadth about 70 % of distance rearward from forehead toward axils of 

 pectorals. Tail moderately stout anterior to spine, but slender thence rearward, tapering 

 to lash-like tip, round to oval in cross section, without fold either above or below; its 

 length from center of cloaca about 2.8 times as great as length of body from cloaca to 

 forehead in small specimens, about twice as long as body in larger ones. 



One tail spine or two,^' the origin of the first (if there are two) immediately posterior 

 to base of dorsal; free portion of longer spine (second in cases seen) about half as long as 

 anterior margin of pelvic fin ; the anterior spine varying in length from so short that its 

 tip hardly emerges from skin to nearly as long as posterior spine; marginal teeth with 

 broad bases and sharp tips, curving rearward at an angle of about 45°; 46 teeth on each 

 side on spine of specimen 755 mm broad but only 22 on one of 550 mm. 



Skin, apart from tail spines, smooth at all ages so far as known. 



Forehead rounded laterally, moderately concave transversely, thus head with sub- 

 rostral fin appears more or less four-lobed. Median belt of upper surface of crown with 

 a shallow longitudinal trough-like depression from level of eyes rearward about as far 

 as level of rear ends of spiracles, much as in Myliobatis (p. 441). Orbits not prominent; 

 eyes close to front of head, approximately circular and noticeably small, their diameter 

 only about ^j^—^jn as great as distance between spiracles. Spiracles about level with orbits, 

 close to them and about ^jc-'^j^ as long. Gill openings weakly sinuous; first to fourth 

 between Vs and ^4 as long as distance between exposed nostrils, fifth a little shorter; 

 distance between inner ends of first gills about twice as great as distance between 

 exposed nostrils; distance between inner ends of fifth gills about 65—70 7o as great as 

 distance between first gills. Nasal curtain of shape shown in Fig. 107 B, its free 

 margin finely fringed with short, simple, rounded lobelets. Mouth nearly straight, 

 occupying a little more than half the width of head, its distance rearward from front 

 of head a little more than half as great as breadth of head at eyes. 



29. One tail spine in four and two in four others of specimens seen; the remaining two complete specimens had lost 

 their spines, leaving only scars. 



