Fishes of the Western North Atlantic 505 



studied), though lacking emergent spines, have a prominent hard rounded protuber- 

 ance or knob on the upper side close behind the dorsal fin and a shallow furrow about 

 as long as the knob immediately behind it. The knob is supported internally by a small 

 fusiform mass of bony tissue, the flattened lower surface of which is attached loosely to 

 the muscular tissue of the tail. And the sloping posterior face of this bony mass bears a 

 minute pointed spur (about Vs •". long on a specimen 1 1 ft. wide) with serrate edges, 

 the tip of which can be felt through the thin overlying skin on both specimens 

 examined. 1" 



Skin of disc, pelvics, and tail generally rough with small tubercles both above and 

 below, without extensive bare areas except for a narrow naked zone along anterior 

 margin of each pectoral ; the tubercles on upper surface of disc and tail, on dorsal 

 fin and on outer faces of cephalic fins ranging from conical to ridge-like on radiate 

 bases, irregularly distributed, their bases nearly touching in some places but wider- 

 spaced elsewhere; tubercles on lower surface about equally large, their bases oval and 

 radially striate, the crests nearly horizontal and vertically truncate posteriorly, their 

 longitudinal axes in general anteroposterior. 



Head with a shallow triangular depression at anterior margin, its base forward; 

 a prominent median crest from nape to shoulder region ; otherwise nearly flat trans- 

 versely; dorsal profile of anterior part of head approximately horizontal antero-poste- 

 riorly; anterior margin between cephalic fins weakly and evenly concave in somewhat 

 half-elliptical outline; its vertical profile above mouth forming a narrow face about 

 5—6 "/o ^s high dorsoventrally as breadth of mouth; lower jaw projecting a little beyond 

 upper anterior margin of head in weakly convex contour, thus conspicuous in dorsal 

 view; margin of lower jaw thick and rounded. 



Eyes high on sides of head and far forward, their centers a little anterior to level 

 of midpoint of front outline of head; round, noticeably small; diameter of exposed 

 eyeball about 5 "/o as great as distance between eyes; pupil round, about 40 "/o ^s wide 

 as width of eyeball. 



Spiracles on upper surface of head, their openings narrow-oval, nearly transverse 

 or weakly oblique with outer ends anterior, about 1.4 times as long as eyeball, each 

 continued outward as a narrowing furrow ending about level with upper edge of eyeball. 



First and second gill openings nearly straight, third to fifth with anterior margins 

 weakly convex rearward; second (longest) about 70 "/o as long as width of mouth; 

 fifth about V3 (67 "/o) as long as second; distance between inner ends of first gills about 

 72 "/o as great as breadth of mouth; distance between inner ends of fifth gills a little less 

 than half as great as distance between first gills; fifth gill openings about half of distance 

 back from front of head toward cloaca. 



Exposed nasal openings a little inward from level of corners of mouth, noticeably 



spine; see also Dumeril (Hist. Nat. Poiss., i, 1865: 661) for a New York specimen about 8 feet 2 inches wide 

 (2,500 mm) with two small tail spines. 

 143. For earlier accounts of specimens without tail spines but with similar knobs, see Mitchill (Ann. New York Lye, 

 I, 1824; 26) and especially Holmes (Proc. Elliott Soc. nat. Hist., i, 1859: 43-44, pi. 31), who has given excellent 

 illustrations of the supporting bony mass with its rudimentary spine. 



