NATURAL SCIENCES OF PHILADELPHIA. 401 



upper jaw. The margin of the upper jaw is somewhat distinctly defined, but 

 not as prominently as in Odontaspis taunts, according to the figure given by 

 Miiller and Henle. The pointed, protruding snout resembles in outline, but 

 is much less prominent than in Eugomphodus griseus, which is the nearest 

 allied species found on our coast. 



A ready point of difference with which to distinguish the Odontaspis Ameri- 

 canus from Eugomphodus griseus, is the position of the second dorsal, which in 

 the former, is anterior to, and in the latter, posterior to the anal fin. 



Teeth, with a single toothlet on either side, but one occasionally wanting. 

 The first tooth in the upper and lower jaws, smaller than the adjoining 

 teeth; then follow, in the upper jaw, on each side, two very long teeth ; at 

 either side of these, another pair of somewhat smaller teeth ; then two teeth 

 increase somewhat in length, then the remainder gradually decrease. 

 In the under jaw from the first pair, the teeth decrease gradually. 

 The fins generally are similar to those of Odontaspis taurus, except the caudal 

 tin, which is very much shorter and broader. 



The posterior margin of the first dorsal in Odontaspis taurus, the nearest 

 allied species, is posterior to the anterior margin of the ventrals, but in Odon- 

 taspis Americanus, the first dorsal is in advance of the ventrals, a distance 

 equal to about half the length of the base of the first dorsal. The same dif- 

 ference exists with reference to the second dorsal and anal, with this species 

 and Odontaspis taurus. 



The head and body, the former especially, are somewhat shrunken and dis- 

 torted by the mounting but the measurements will be found nearly correct. 

 Those measurements unattainable are marked approximating. 



Total length 105 inches. 



Tip of snout to nostril, approximating 5 " 



Nostril to mouth, approximating Sh " 



Mouth to anus, approximating 6(T " 



Anus to anal fin, approximating 12 " 



Base of anal fin 5 " 



Anterior margin of anal fin 5 " 



Anal to caudal fin 31! " 



Length of caudal fin, ant. inser. to extremity 22 " 



Anterior margin of underflap of caudal 8 " 



From pectoral to ventral 25 " 



Post. bord. of pec. to ant. bord. of first dorsal 25 " 



Base of first dorsal *jx << 



Anterior margin of first dorsal 8 " 



Post, margin of first dorsal to ant. margin of ventrals llf " 



Base of second dorsal 51 " 



Anterior margin of second dorsal 7 " 



Base of ventrals 8i " 



Anterior margin of ventrals Q* " 



Distance between nostrils, approximating 3 " 



Width of mouth, angle to angle 9| " 



Margin of upper jaw 171. 



Margin of lower jaw 13 



8 



<( 



The specimen described was taken off " Beesley's Point," coast of New 

 Jersey, by Messrs. R. Stites, S. Ashmead and Dr. Leidy. 



According to Dr. Mitchill, this shark was at one time, one of the most 

 abundant species, but at present, judging from the fact of the species remain- 

 ing so long undetermined, it must be a rare representative of the Squalida 

 on the Eastern Coast of North America. 



1861.] 27 



