FISHES — SPINACIDAE— ACANIHIAS. 367 



edge is strong, the inner edge being finely serrated towards the base. The foremost teeth con- 

 stitute a group, are hook-shaped, with a broader base. The adjoining ones are provided exte- 

 riorly with one or more lateral prongs. The outermost teeth are like those at the lower jaw. 

 The body is elongated and fusiform, with a conspicuous lateral line. There is but one dorsal 

 fin, situated between the ventrals and the anal, and partly opposed to the latter. Caudal fin 

 with a small lower lobe emarginated towards its extremity, the posterior margin being oblique 

 or straight and truncated. The caudal grooves or furrows are wanting. The intestinal valve 

 is helicoid. 



Stn.— JVi)(irfamnt, Bonap. Syst. Vertebr. 1837, 45; &, Selacli. Tabiil. analyt. 1838, 4. 



J\''oii(lani, Mcll. & Henle, Syst. Bcsclir. Plagiost. 1841, 8(1 — Mull, in Wiegm. Archiv fur Naturg. 1845,1, 137. — 



- Bd. Iconogr. Encycl. II, 1850, 242.— Drw. Ichthyol. analyt. ]8.'")G, 133. 

 J^olidanidae , Owen, Lect. Corap. Anat. Vertebr. Aiiim. 1846, 51. 



When the branchial apertures are six on either side we have the genus Hexanclms ; and when 

 seven of them exist, the genus Heptanclius {Hejotranchias) . These were the only two genera 

 of the family described by ichthyologists. 



A shark of this family having recently been observed in the bay of San Francisco, California, was 

 erroneously erected into a third genus, under the name of Notorhynchus, v/hich does not differ 

 from Heptanchus. We will therefore record the species under the appellation of 



HEPTANCHUS MACULATUS, G r d . 

 Stn. — Motorhynchus maculatus, Atres, in Proc. Cal. Acad. Nat. Sc. I, 1855, 72. 



In the absence of specimens we forbear drawing up a specific description, and refer our readers 

 to the above quoted " Proceedings of the California Academy," in which Dr. Ayres has recorded 

 the observations he has traced from nature. 



Family SPJNACIDAE, Owen. 



The sharks which constitute this family exhibit two dorsal fins, whilst the anal is wanting, 

 either dorsal being provided with a strong spine at its anterior margin, as is likewise the case 

 in Cestraciontidae. The spiracles are extant, and the five branchial apertures situated in ad- 

 vance of the pectoral fins. The nictitating membrane of the eye is wanting. The intestinal 

 valve is helicoid. 



SvN. — Spinaces, Mull. & Henle, .Syst. Beschr. Plagiost. 1841, 83. — Mull, in IViegm. Archiv fiir Naturg. 1845, I, 135 

 & 137.— DuM. Ichthyol. analyt. 1856, 133. 



Spinacini, Bonap. Syst. Vert 1837, 4. — Bd. Iconogr. Encyl. U, 185(1, 242. 

 Spirtttcidae, Owen, Lect. Comp. Anat. Vertebr. Anim. 1846, 51. 



Some of the representatives of this family are commonly known under the names of " Dog- 

 fish" and "^ Picked Dog-fish," both in England and in America, being distinguished from il/ws- 

 telidae, which go under the same vernacular appellation on this side of the Atlantic, by the 

 presence of a rather strong spine at the anterior margin of the dorsal fins. 



ACaNTHIAS, Uisso. 



Gen. Char — Head depressed. Outline of the mouth in the shape of a very open curve; a large groove at either angle. Two 

 carlilaginous folds of the lips anteriorly (superiorlv) and one posteriorly (inferiorly) . Spiracles very large, situated behind and 

 somewhat above the eyes, and provided within with a swelled flap arising from their anterior margin. Orbits elongated; upper 

 and lower teeth cutting, the edge being nearly horizontal and the point directed outwardly. Tlio root of the tooth is more 



