494- PROCEEDINGS OF THE ACADEMY OF 



Caudal fin elongated, with the anterior lobe in front produced downwards 

 and nearly rectangular, and with the terminal one distinct and acutely trian- 

 gular. 



Pectoral fins moderate, trapezoid produced towards its external terminal 

 angle. 



Ventral fins oblong, emarginated along its external border, acutely produced 

 at its inner or produced angle. 



This generic name of Notorhynchus was proposed by Dr. Ayres, under a mis- 

 apprehension, for a species which is congeneric with one regarded by all pre- 

 vious naturalists as a species of the genus Heptanchus. After an examination 

 of the jaws of a shark presumed to belong to the species noticed by Ayres, and 

 presented at Nisqually to one of the representatives of the Exploring Expedi- 

 tion under Commodore Wilkes, I am compelled to believe that such species 

 Bhould be separated from Heptanchus. The name of Ayres must, then be 

 adopted for the genus embracing that species. 



Notorhynchus may be briefly characterized as a Hexanchus in form and den- 

 tition with the seven branchial apertures of Heptanchus. If the totality of 

 its character is considered to be of more importance than the number of bran- 

 chial apertures, Notorhynchus is then more closely related to Heptanchus, 

 having the same form of the head and the same dentition, while it agrees with 

 the latter only in the number of its branchial apertures. 



In addition to the type of the genus, that species of the East Indian Seas first 

 made known by Muller and Henle under the name of Heptanchus indicus must 

 be referred to Notorhynchus. Like Notorhynchus maculatus, the East Indian 

 species is spotted, and although it appears to differ considerably from the for- 

 mer in dentition, that difference cannot be regarded as being of more than spe- 

 cific importance. 



The d fferences in the dentition of the genera Heptanchus and Notorhynchus 

 principally refer to the relative development of the teeth of the lower jaw and 

 their armature. In Heptanchus, the developed teeth on each side of that jaw 

 regularly increase in breadth from the symphysis towards the corners of the 

 mouth, the inner cusp is much enlarged, and its ascending or inner 

 margin is armed with one or two smaller cusps. The median tooth of 

 the lower jaw is also well developed and has a central acute cusp. In Noto- 

 rhynchus, on the contrary, the teeth of the lower jaw are either uniform or de- 

 crease towards the corner of the mouth, the cusps on the oblique cutting mar- 

 gin are regularly graduated, while the ascending inner margin of each tooth 

 is finely serrated. The median tooth is also emarginated instead of cuspidate 

 at its own middle. The difference between the teeth of the upper jaw in the 

 respective genera is of much less importance. 



The typical or Califoruian species of Notorhynchus is closely related to the No- 

 torhynchus indicus, but is at once distinguishable by its dentition, the teeth of 

 the lower jaw being comparatively broader and less elevated, and armed with 

 six or 6even points instead of five, and there being no very prominent denti- 

 cles on the inner margin of the upper teeth near the front ones as there are in 

 those of N. indicus. The dorsal appears also to be nearer the snout than it is 

 in its Indian representative. 



The Notorhynchus maculatus is said by Ayres to be " apparently not un- 

 common in the Bay of San Francisco, at certain seasons of the year." It at- 

 tains to a length of six or seven feec, and is used as food by the Chinese in- 

 habitants of California. 



It will be necessary to bear in mind that the description of the den'ition of 

 Notorhynchus maculatus is based on the jaws of a specimen obtained at Nis- 

 qually by the Exploring Expedition under Commodore Wilkes. There can be 

 little doubt as to the specific unity of the different materials, but as Dr. Ayres' 

 notice of the dentition is equally applicable to any species of the family, the 

 correctness of this identification still requires to be verified. 



[Oct. 



