NOTORYNCHUS PLATYCEPHALUS. 19 



Heptranchias maculalus Gill, 1861, Ann. N. Y. lye, 7, p. 404; Jordan & Gilbert, 1880, Proc. U. S. nat. 



mus., 3, p. 353; 1883, Bull. 16, U. S. nat. mus., p. 62. 

 Nolorhynchus maculalus Gill, 1862, Proc. Acad. nat. sci. Phil., p. 495; 1864, ibid., p. 150; Jord. & 



EvERM., 1896, Bull. 47, U. S. nat. mus., p. 17; 1900, ibid., Atlas, pi. 2, f. 7. 

 Nolorhynchus borealis Gill, 1864, Proc. Acad. nat. sci. Phil., p. 150. 

 Notidanus plalycephalus Gunth., 1870, Cat. fishes Brit, mus., 8, p. 398. 



Form moderately elongate, depressed anteriorly, compressed backward, 

 much resembling that of Hexanchus griseus; body cavity less than half the total 

 in a specimen two feet in length. Head more than five times in the total, broad, 

 depressed, slightly convex on the crown; snout broad, blunt. Eyes medium, 

 half as long as the snout, lateral. Nostrils anterior, near the end of the snout. 

 Spiracles small, far behind the eye. Mouth large, more than twice as wide as 

 long, broadly arched in front. Teeth compressed in cusps and bases; no median 

 tooth in the upper series; at each side of the symphysis there is a pair of small 

 teeth with indistinct basal denticles; at the outer side of these on the six lateral 

 teeth the primary cusp becomes more oblique and the denticles at its base 

 increase in size and number which causes them to resemble more and more the 

 lateral teeth of the lower jaw, though there is more difference in size between 

 the primary cusp and the two to five at its outer side; a median tooth on the 

 lower jaw, more often without a median cusp, is followed by six large laterals 

 on which there are from three to six cusps beside the primary cusp, which latter, 

 as in the upper teeth, is denticulate or serrate on its inner edge; at the angle of 

 the mouth behind the pectinate teeth there are from six to eight rows of small 

 elongate low-crowned teeth remotely resembling those of species of Hybodus 

 or Acrodus. A distinct lower labial fold at the angle of the mouth. As this 

 fold contains the labial cartilages it is evident that the edge of the groove behind 

 the angle is a different structure. The upper extremity of the labial fold encloses 

 a blind sac of considerable size extending toward the eye. Gill openings seven, 

 large, in front of the pectoral. 



Pectorals large, nearly as broad as long, hind margin concave. Dorsal 

 small, hardly as large as the ventrals, originating above or little forward of the 

 ends of the ventral bases, hind angles acute. Anal smaller than the dorsal, 

 origin little forward of the end of the latter's base; anal base one and one third 

 times its length forward of the origin of the caudal. Caudal fin very long, on 

 young nearly two and one half times in the total length, subcaudal slightly 

 produced in an angle anteriorly, narrow and separated from the tip by a notch 

 posteriorly; tip pointed; upper edge, in young stages, armed with modified 

 scales. 



