go Memoir Sears Foundation for Marine Research 



Interspace between: ist dorsal and caudal 14.2, 14.8; anal and caudal 9.0, 9.7. 



Distance from origin to origin of: pectorals and pelvics 18.9, 22.0; pelvics and 



anal 15.0, 15.0. 

 Trunk rather slender, compressed, its height at about midsection of body, where 

 highest, 1 1.6 to 1 1.8% of total length, the body sector shorter than tail sector by a distance 

 about equal to length of pectoral. Caudal peduncle about 75 to 80% as wide as deep; no 

 precaudal pits. Dermal denticles on sides of trunk closely overlapping, a little longer than 

 broad, each denticle with prominent median tooth, flanked by a pair of much smaller lat- 

 erals, a strong median ridge and upturned lateral edges, the blades so thin and transparent 

 that the pigment dots on the skin are visible through them; those along upper margin of 

 caudal ovoid, without lateral marginal teeth, but with 3 longitudinal ridges, the median 

 subdivided posteriorly, forming an ill-defined crest, much as in Hexanchus griseus (p. 



81). 



Head with dorsal profile slightly convex. Snout tapering, narrow, its tip slightly 

 rounded. Eye notably large (as in Hexanchus), oval, its anterior edge about opposite front 

 of mouth. Spiracle minute, about on level with upper edge of eye, its distance behind eye 

 about equal to horizontal diameter of latter. Gill openings extending down onto throat, the 

 1st about I V2 times as long as horizontal diameter of eye, the 2nd to 7th decreasing succes- 

 sively in length, the 7th only about Y2 as long as ist. Nostril about equidistant between 

 mouth and tip of snout, its anterior margin expanded as a broadly triangular, corrugated 

 lobe (Fig. 10 B). Mouth narrowly rounded in front, notably long, the length about equal 

 to breadth, with very extensive gape, lateral in position for most of its length, the margin 

 of upper lip extending rearward past corner of mouth for a distance equal to V2 to % 

 horizontal diameter of eye. An oblique labial furrow at angle of mouth, originating on 

 upper jaw and extending downward and forward for a short distance onto lower jaw. 



Teeth ^zE^i ^^ grown specimens, ^'""j^" in young of 257 mm., unlike in the 2 jaws; 

 upper teeth fang-like, strongly oblique, the first 3 or 4 more or less sinuous in outline 

 with base as well as cusp smooth-edged, but subsequent upper teeth with i or 2 small 

 subsidiary cusps at base on inner side and i on the outer, the outermost upper tooth low, 

 without definite cusp; lower jaw with i symmetrical tooth at symphysis with large me- 

 dian cusp, and i or 2 smaller on either side, the lateral lower teeth very broad and low, 

 each with a series of 6 to 8 somewhat oblique triangular cusps in male, and 7 to 10 in 

 female, the 2nd or 3rd of which is much the largest, their edges perfectly smooth; 2 to 3 

 series of teeth functional in front of upper jaw and i along sides; i series functional in 

 lower jaw. 



Origin of dorsal a little posterior to cloaca, its anterior margin straight or slightly con- 

 vex, its apex broadly rounded, its rear margin concave, its free rear corner prolonged a 

 distance equal to about V^ the horizontal diameter of eye, its vertical height about Vs ^s 

 great as length of pectoral. Interspace between dorsal and caudal about as long as between 

 axil of pectoral and origin of pelvics. Axis of caudal hardly raised, its upper margin mod- 

 erately convex, lower margin with well marked subterminal notch, rather strongly concave 



