ORDER VIII. 



HOLOCEPHALI. 



The skeleton is cartilaginous, and reduced to a soft vertebral chord. The teeth consist of large 

 plates resting upon the jaws, which do not exist as separate pieces, being continuous with the rest of 

 the uninterrupted bones of the skull. The gills are laminated, attached by their margins ; with 

 a single external aperture on either side. There is no swimming or air bladder, but the intestine 

 is provided with a spiral valve. The sexes copulate. A spinous ray may be observed at the an- 

 terior margin of some of the fins. The ventrals are inserted behind the pectorals. The dermic 

 productions, when existing, are of the placoid type. 



Syh .—Holocfphali, Ml'll. Vergl. anat. Myxin. in Abhandl. Berl.Akad. (1834), 1836; &, in Wiegm. Archiv fur Naturf. 

 1845, I, 137 & 135.— Owen, Lcct. Conip. Anat. Vert. anim. '.846, 50.— Bd. Icongr. Encycl. II, 185U, 205. 



This order is composed of two families — that of Chimaeridae, with a few living representa- 

 tives, and that of Edaphodontidae, whose types are all extinct. 



Family CHIMAERIDAE, Bonap. 



The body is somewhat elongated, compressed, and tapering gradually from the thoracic belt 

 to the filamentous termination of the caudal extremity. There are two dorsal fins, the first one 

 provided anteriorly with a spine dentated upon its posterior or inner edge. The second dorsal 

 fin is generally low and elongated ; the lobes of the caudal are lower still, rather elongated 

 also, the upper lobe having been taken for a third dorsal fin and the lower lobe for an anal fin 

 by Linnaeus and some of his followers. The anal fin, properly so called, is sometimes wanting 

 and sometimes existing. The insertion of the ventral fins takes place either anteriorly or poste- 

 riorly to the middle region of the abdomen ; the organs of generation so constructed as to in- 

 volve a union between the sexes, in order to accomplish the act of fecundation, and hence of 

 reproduction. 



Syn. — Chimaeridae, Bonap. Sagg Distr. melod. anim. Vert. 1831, 121. — Benn. in Zool. Beechey's Voy. Blossom. 1839, 71. 

 Chimerides, Agass. Rech. Poiss. foss. Ill, 1842, 336. 

 Chimaerae, Mill, in Wiegm. Archiv fur Naturg. I, 1845, 137. 

 Chimaeroidei, Owen, Lect. Comp. Anat. Vert. anim. 1846, 51. — Bd. Iconogr. Encycl. II, 1850, 205. 



There are but two living genera known up to the present day as con.stituting this family — 

 Chimaera, the species of which belong to the northern hemisphere, and Callorhynchus, the 

 species of which belong to the southern hemisphere. 



CHIMAERA, Linn. 



Gen. Char. — Mouth situated beneath the snout, which is sub-conical. Teeth well developed. Nostrils immediately in 

 advance of the mouth, and extending into it. One branchial split on either side, separated under the throat by an isthmus. 

 Two dorsal fins — anterior one situated above the pectorals, and provided with a strong spine ; caudal, tapering into a point ; 

 anal fin wanting ; ventrals nearly median, situated opposite the beginning of the second dorsal. Skin smooth. 



Syk.— Chimaera, Linn. Syst. Nat.ed. XIl^ I, 1766, 401.— Gmel. in Linn. Syst. Nat. ed. XllJa I, iii, 1788, 1488.— Cov. 

 Rfegn. anim. II, 1617, 140 ; 2d ed. II, 1829 ; &, ed. illustr. Poiss. 354. 



