458 Memoir Sears Foundation for Marine Research 



Trunk very slender, its height at ist dorsal only about Vr its length to origin of 

 caudal, its dorsal profile sloping forward from ist dorsal. Body sector to cloaca longer than 

 tail sector by a distance about % as long as head, and without mid-dorsal ridge. Caudal 

 peduncle flattened below but rounded above, with a low rounded longitudinal dermal ridge 

 along each side a little below the midlevel, which extends from a little behind base of 

 2nd dorsal to beyond origin of caudal. Upper precaudal pit subrectangular, more or less 

 strongly developed, although some specimens appear to lack it 5 no lower pit. Dermal denti- 

 cles Idosely spaced and exposing the skin, rising steeply over the trunk as a whole but lying 

 flat and in close contact (overlapping only a little if any) on top of snout and along edges 

 of fins J essentially spine-like but somewhat expanded laterally, the terminal portion 

 mostly a little longer than broad with a strong flat-topped median ridge, but varying con- 

 siderably in shape on difi"erent parts of the body; those on sides and back posterior to ist 

 dorsal fin as well as on upper surfaces of pectorals more or less definitely tridentate (me- 

 dian tooth much the largest), but interspaced here and there with faintly tridentate forms; 

 those on top of head less strongly tridentate, interspersed with broad-lanceolate; those on 

 lower surface weakly tridentate anteriorly, but mostly very narrow-lanceolate posteriorly, 

 without definite lateral teeth; those on sides of ist and 2nd dorsals broad-lanceolate and 

 but faintly ridged; those on top of snout and along anterior margins of fins broad-oval and 

 smooth, or very faintly ridged.'^ 



Head about V4 of trunk to origin of caudal, moderately flattened above. Snout rather 

 thick, ovate, with rounded tip, its length in front of nostrils a little more than Vs its length 

 in front of mouth, its length in front of mouth a little less than ^ (about 43 to 44%) of 

 length of head. Eye a little longer than high, its upper outline less convex than its lower, 

 its horizontal diameter a little more than V3 as long as snout in front of mouth or about 

 the same as distance between nostrils; relatively a little larger in newborn specimens than 

 in adults. Spiracle close behind eye, about Vs as long as horizontal diameter of eye, its 

 lower margin about level with upper margin of latter or a little above it. Gill openings 

 low down on sides, the ist to 4th about evenly spaced, but the 5th closer to 4th; the ist to 

 4th about same length, the 5th the longest, the latter about % as long as horizontal diam- 

 eter of eye or a little less than % as long as snout in front of mouth and i Vs times as long 

 as 1st; the 5th close in front of origin of pectoral. Nostril approximately transverse, its 

 inner end a little nearer to tip of snout than to symphysis of upper jaw, its anterior margin 

 expanded as a simple, subtriangular lobe. Mouth only very slightly arched. Upper labial 

 furrow extending inward and forward for a distance about V2 as long as diameter of eye, 

 the lower furrow V2 to % as long as upper. 



'^^^'•'^ iior 12— — i iori2 ^'^ specimcns counted, essentially similar in the two jaws, 

 smooth-edged, with single sharp-pointed cusp, deeply notched outwardly and so strongly 

 oblique that the inner margins form a nearly continuous cutting edge from one corner 

 of the mouth to the other; the lowers somewhat larger than uppers, and considerably 



24. For a more detailed account and discussion of the denticles, see Sayles and Hershlowitz (Biol. Bull. Wood's Hole, 

 73, 1937: 5)- 



