Myxinoids, an order of fishes, which, with the cyclostomes or lampreys, form the class of myzonts of Agassiz, containing the lowest of the vertebrates. They form the family hy-perotreta (Mull.; marsipohranchii of Huxley), and are characterized by a cylindrical body, obliquely truncated anteriorly; the mouth is furnished with cirri or tentacles, the palate is perforated, and the cavities of the nose and mouth communicate (as in no other fish); the upper margin of the mouth has a single tooth, and the tongue has a double recurved row on each side; the jaws are absent, and the inferior margin of the mouth is formed by the anterior extremity of the tongue bone; the eyes are concealed; the branchia3 are on each side, with internal ducts leading to the oesophagus. For full details see the papers of J. Müller in the " Transactions of the Berlin Academy" for 1834, 1838, 1839, and 1842, and papers by F. W. Putnam in "Proceedings of the Boston Society of Natural History," vol. xvi., 1874. In the genus myxine (Linn.) two spiracles approximate on the lower surface behind the branchiae, each receiving the external ducts of the six branchiaa of its own side.
The common myxine or glutinous hag (M. glutinosa, Linn.) has a smooth eel-like body, with a very long dorsal fin continued round the tail to the vent, a single spiracle on the head, and eight barbules around the mouth; the color is bluish brown above and whitish below; the length is from 0 to 15 in. Linnaeus placed this animal among worms, regarding the two lateral parts of the tongue as transverse jaws, which do not occur in vertebrates, it is the lowest of vertebrates, except the lancelet. The specific name is derived from the great quantity of viscid mucus secreted by the cutaneous glands whose pores open along the under surface of the body; the spinal column is a soft and flexible cartilaginous tube, with no division into rudimentary vertebrae. It is called borer from its habit of eating into the bodies of other fish which have been caught on hooks, entering the mouth or other part of the surface, and in this way is often annoying to fishermen during spring and summer. It is found along the coasts of Great Britain and in the northern seas, on the N. E. coast of North America, and the S. coast of South America. In the genus heptatrema (Dam.) or Mellostoma (Mull.) there are six or seven branchiae on each side, each with an external spiracle; the eyes are very small, conspicuous through the skin.
It resembles the preceding genus in internal structure, and attains a larger size; it is found in the southern seas, preferring rocky bottoms, where it lies in wait for fishes; it is active, and has remarkable powers of emitting mucus from the skin. The species described as bdel-lostoma Forsteri by Müller and as B. cirrha-tum by Günther is roasted and eaten by the natives of New Zealand.
Organs of Eespiration in the Myxine: a, single hooked tooth; bbbb, double rows of lingual teeth; c, branchial cells; d d d d, tentacula; e, mucous glands.
Common Myxine (Myxine glutinosa).