MYXIXID-S. — II. 



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. kvkXos, circle ; 

 0-Tci/na, 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 (.lose behind 

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



Order II. HYPEROTRETA. 



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

 rprjTos, perforate.) 



Family II. MYXINID^E. (Tin: 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 .'>. Lamprey- 

 like animals, burrowing into the llesh of fishes, on which they feed ; 

 marine. 



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

 sacs Myxixe, 2. 



2. MYXIITI3 Linnreus. (Gr. piga, slime.) 



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

 in length. X. AtL, S. to Cape Cod. (Eu.) 



