MYXINIDA, — IL 9 
Crass D. CYCLOSTOMI. (THE Myzonrts.) 
Skeleton cartilaginous; skull imperfect, not separate from ver- 
tebral column; no jaws; no limbs; no ribs; no shoulder girdle nor 
pelvic elements ; gills in the form of fixed sacs, 6 or more on each 
side; nostril single, median; mouth subinferior, nearly circular, 
adapted for sucking; heart without arterial bulb; alimentary 
canal straight, simple ; vertical fins with feeble rays. Naked, eel- 
shaped animals found in all cool waters. (Gr. xv«dos, circle; 
ordza, mouth.) 
Orders of Cyclostomi. 
a. Nostril tube-like with cartilaginous rings, penetrating the palate; gill 
openings remote from the head; no eyes.. . . . HYPEROTRETA, 2. 
aa. Nostril a blind sac not entering the palate; gill openings close behind 
the head; eyes well developed in the adult... . HYPEROARTIA, 2. 
Orvrer I. HYPEROTRETA. 
Characters as given above. Only one family. (izepea, palate ; 
tpytés, perforate.) 
Famity Il. MYXINIDAX. (Tue Hac-risues.) 
Snout with eight barbels; no lips; a median tooth on the palate 
and two rows on each side of the tongue, which is a powerful organ 
with a strong fibrous tendon moving in a muscular sheath; each 
side of abdomen with a series of mucous sacs; no eyes; intestine 
without spiral valve; skin thin and loose; eggs large, with a horny 
case and threads for adhesion; genera 2; species 4 or 5. Lamprey- 
like animals, burrowing into the flesh of fishes, on which they feed ; 
marine. 
uw, Gill openings one on each side, this leading by six ducts to six branchial 
Bee ce eR ee we ee ee we ee ee we em 6 Mie, 2, 
2. MYXINE Linneus. (Gr. pvéa, slime.) 
2. M. glutinosa L. Hac-risu, Borer. Bluish; head 33 to 4 
in length. N. Atl, S. to Cape Cod. (Eu.) 
