MYXINID^. — U. 



Class D. CYCLOSTOMI. (The Myzonts.) 



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. kvkKos, circle ; 

 <TT6iia, mouth.) 



Orders of Gyclostomi. 



u. Nostril tube-like with cartilaginous rings, penetrating the palate; gill 



openings remote from the head; no eyes Hyperotreta, 2. 



oo. Nostril a blind sac not entering the palate ; gill openings close behind 

 the head ; eyes well developed in the adult. . . . Hypekoaktia, 2, 



Order II. HYPEROTRETA. 



Characters as given above. Only one family, (itrepioa, palate ; 

 TprjTds, perforate.) 



Family II. MYXINID^. (The Hag-fishes.) 



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. 



o. Gill openings one on each side, this leading by six ducts to six branchial 

 sacs Myxine, 2. 



2. MYXINE Linnaeus. (Gr. pv^a, slime.) 



2. M. glutinosa L. Hag-fish, Borer. Bluish ; head 3^ to 4 

 in length. N. Atl., S. to Cape Cod. (E«.) 



