364 
U. S. P. E. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
Family MUSTELIDAE^ Girard. 
The spiracles are very large; the orbits elongated ; the nictitating membrane ridge-like, 
appearing as though a duplicature of the lower eyelid. The teeth are pavement-like, depressed, 
without points or cutting edge, in which respects they resemble those of the rays or skates. 
Angles of the mouth protuberant and cartilaginous, with deep grooves. The upper (anterior) 
edge of the nostrils provided with a triangular membranous flap, rounded upon its terminal 
extremity, whilst its base occupies the three-fourths of the nasal edge. Exteriorly to this is a 
shorter and more truncated or blunt flap. The last branchial fissure is situated above tbe base 
of the pectoral fins. The first dorsal fin is situated nearly midway between the pectorals and 
the ventral fins. The caudal fin is rather short, the caudal furrows being inconspicuous. 
Intestinal valve helicoid. 
Syn. — Mustelini, Bonap. Sjst. Vertebr. 1837, 45 ; &, Selach. Tabul. analyt. 1838, 5.—Bn. Icongr. Encycl. II, 1850, 241. 
Musteli, Mull. & Henle, Syst. Beschr. Plagiost. 1841, 64 .—Dum. Ichthyol. analyt. 1856, 130. 
The genus Mustelus is the only representative of this family, its species occurring in the 
Mediterranean sea and in both the Atlantic and Pacific oceans. The one which is met with 
along our Atlantic coast is commonly known as the “dog-fish,” “ hound-fish,” or “dog-fish 
shark.” These sharks do not reach any very large size. 
A species has recently been found along the Pacific coast, about the bay of San Francisco, and 
described under the name of 
MUSTELUS FELIS, Ayres, 
in the Proceedings of the California Academy of Natural Sciences, I, 1854, 17, and, since we 
had no opportunity of studying it from nature, we are compelled to dismiss it with the above 
few remarks. 
Family CESTRACIOAILDAE, Owen. 
The mouth approximates the anterior margin of the snout, the nostrils extending to the 
mouth, through a cleft of the anterior or upper lip. The spiracles are conspicuous. The bran¬ 
chial apertures are small, the hind ones being situated above the base of the pectoral fins. A 
spine at the anterior margin of the dorsal fins. The caudal fin is short, with a slight emargi- 
nation between either lobe at the posterior margin. 
The division of sharks to which this family belongs are provided with two dorsals and one 
anal fin, the first dorsal fin being placed between the pectorals and the ventrals. The nicti¬ 
tating membrane is wanting, whilst the spiracles exist. 
Syn. — Cestraciontes, Agass. Rech. Poiss. foss. Ill, 1833, 173.— Mull. & Henle, Syst. Beschr. Plagiost. 1841, 76.— Dum. 
Ichthyol. analyt. 1856, 132. 
Cestraciontini, Bonap. Syst. Vert. 1837, 46. 
Cestracionini, Bonap. Selach. Tabul. analyt. 1838, 5.— Bd. Inconogr. Encyl. II, 1850, 242. 
Cestraciones, Mull, in Wiegm. Archiv fur Naturg. I, 1845, 137. 
Cestraciontidae, Owen, Lect. Comp. Anat. Vert. Anim. 1846, 51. 
The genus Cestracion is the only one so far known ol the family. The species that have been 
noticed are but few in number, and scattered over a wide geographical range. 
