82 Memoir Sears Foundation for Marine Research 



only about Y^ as great as breadth of mouth. Eye oval and noticeably large, its horizontal 

 diameter about Yj as great as length of head in a 2^/'o-foot specimen, but perhaps relatively 

 smaller in adults." Spiracle very small, at level of upper margin of eye, about opposite 

 corner of mouth. Gill openings notably long, extending from high on sides far onto ven- 

 tral surface of throat, and noticeably oblique, the ist (longest) about 2V2 times as long as 

 horizontal diameter of eye, successively shorter, rearward, the 6th only a little more than 

 Y2 as long as the istj the inner margins of 2nd and 3rd gill arches with 2, and 4th to 6th 

 with 3 to 5, fleshy tubercles, suggesting rudimentary rakers. Nostril much nearer to tip 

 of snout than to mouth, small, strongly oblique, its anterior margin expanded as a sub- 

 triangular lobe with blunt tip. Mouth notably large, about % as high as broad, crescentic 

 and inferior anteriorly, but extending along sides of head for most of its length, the gape 

 reaching rearward about % of distance to origin of pectoral. Well developed labial furrow 

 at corner of mouth on lower jaw, visible only when mouth is partly open; none on upper 

 jaw. Upper lip enclosing posterior part of lower jaw as a free fold extending rearward 

 past corner of mouth for a distance about equal to horizontal diameter of eye. 



Teeth — — ; noticeably diflFerent in the 2 laws; ist 2 to 



i2toi6 — I (or 0) • — i2toi6 ' •' 



4 uppers simple with slender median cusp curved outward, the ist noticeably smaller, the 

 2nd slightly smaller and with narrower bases than 3rd, the subsequent teeth to the lOth 

 or nth with i, 2 or 3 short basal cusps on outer side (number increasing toward corner of 

 mouth and with growth), the outermost 7 or 8 teeth rounded, with only very small cusp 

 or none, and much lower than the others. Lower jaw usually with i symmetrical median 

 tooth, having i median cusp and i, 2 or 3 lower cusps on each side," the next 6 (occasion- 

 ally 5) teeth trapezoid, about twice as broad as high, with 7 to 8 pointed cusps in small 

 specimens, increasing in number to 8 to 10 in large, the innermost cusp the longest, the 

 others progressively shorter, the inner margins smooth in newborn specimens, but finely 

 serrate in large, with intermediate sizes showing intermediate states,'^ the 7th lower tooth 

 (6th in specimens which have only 5 large laterals) much smaller, with only i definite 

 cusp, the outermost 4 to 6 teeth very low, rounded, without cusp ; 2 or 3 series functional in 

 center of upper jaw and i along its sides; i series functional in lower jaw. 



Vertical fins small. Dorsal with rounded apex and weakly convex rear margin, free 

 rear tip broadly triangular, about half as long as base, its origin slightly behind cloaca, 

 the midpoint of its base about over origin of anal. Caudal about Vs of total length, with 

 well marked subterminal notch, its lower anterior corner expanded as a low rounded lobe 

 in newborn but not appreciably so in larger specimens (cf. Fig. 8 A and 9 A), its maximum 

 breadth a little more than Ys its length. Anal about as long at base as ist dorsal, rear margin 

 nearly straight, free rear tip short. Interspace between rear end of base of anal and origin 

 of caudal about Y2 as long as between dorsal and caudal. Pel vies with nearly straight mar- 



1 1. The eye, as in many sharks, is relatively larger in newborn than in older specimens. 



II. This median tooth is lacking in the small Mediterranean specimen listed under Study Material, p. So. 



13. For further details, see discussion, p. 79. 



