I02 Memoir Sears Foundation for Marine Research 



pressed. Dermal denticles about 0.4 mm. broad, by 0.45 mm. long in a specimen of about 

 100 cm. length, loosely spaced, their blades ovoid lanceolate, their anterior margins en- 

 tire or slightly indented between tips of the 3 ridges; axial ridge very prominent and 

 sharp-edged anteriorly but usually flat-topped and subdivided posteriorly. 



Head moderately flattened above. Snout short, its length in front of mouth about V4 

 to Vs the length to ist gill slit, narrow ovoid, with rounded tip. Eye round and small, its 

 diameter only about % as long as distance between nostrils. Spiracle minute, about on a 

 level with upper margin of eye and behind latter by a distance about equal to length of 

 snout in front of mouth. Gill openings relatively large, 4th about as long as snout in front 

 of mouth, others slightly shorter, the 5th shortest. Nostril nearly transverse, its anterior 

 margin with a small rounded flap near inner end. Distance from inner angle of nostril to 

 mouth about equal to width of nostril. Mouth crescentic in front, about % to % as long as 

 broad; angle of mouth with well marked labial furrow on lower jaw and a less prominent 

 one on upper; upper furrow partially hidden when mouth is closed. 



Teeth l\ |° H m specimens examined, ist to 6th or 7th teeth in each jaw either with 

 or without i or 2 small basal denticles on either side;'° ist upper tooth usually a little 

 smaller, but sometimes of the same size as 2nd or 3rd, the 4th much smaller than 3rd 

 or 5th, with a broad interspace between 4th and 5th} ist lower tooth much smaller than 

 2nd to 6th, the teeth posterior to 6th or 7th successively smaller in each jaw and broader 

 relative to length, with denticles successively larger relative to median cusp, the outermost 

 12 or 13 minute, close set, tricuspidate, about as broad as high; 3 or 4 series functional 

 toward corners of mouth, but only i or 2 series toward center." 



Origin of ist dorsal about midway between axil of pectoral and origin of pelvics, its 

 base terminating a little anterior to latter, its apex subacute, its rear margin slightly concave, 

 the free corner about Vs as long as its base, its vertical height about V2 as great as length of 

 pectoral or about V4 as great as length of head. Second dorsal similar to ist and only 

 slightly smaller, its origin about midway between cloaca and origin of anal, Y^ to V2 of its 

 base overlapping base of latter. Caudal about 30% of total length, its axis only slightly 

 raised, the subterminal notch well marked, the posterior outline of terminal sector con- 

 cave, its lower anterior corner expanded as a definite lobe with rounded apex, its anterior 

 margin about Vs as long as upper caudal margin; re-entrant corner, included between the 

 2 lobes, broadly rounded. Anal a little larger than 2nd dorsal in area and a little longer 

 basally, its rear margin less deeply concave, its free rear tip about Vs as long as its base, 

 the interspace between anal and caudal only about V2 as long as base of anal. Pelvics origi- 

 nating a little posterior to rear end of base of ist dorsal, and about as large as latter, the 

 inner margins entirely separate posterior to cloaca in female, but connected for a short 



16. On a large New Jersey specimen every tooth, from the first to the seventh, is flanked by one or two denticles 

 on each side; in another, from southern Massachusetts, the fourth upper tooth lacks a denticle, while on still 

 other specimens from the same general locality some of the teeth have a denticle on each side, some have a den- 

 ticle on one side only, and still others have no denticle on either side. 



17. An account of the shedding of the teeth of specimens in an aquarium is given by Breder (Copeia, 1942: 42) ; 

 see also p. 65. 



