MYXINIDA.—IL a 
Cirass 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. kudos, circle; 
oTdéua, 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.. . . HyYPEROARTIA, 2. 
OrvER II. HYPEROTRETA. 
Characters as given above. Only one family. (depda, palate ; 
tpntos, perforate.) 
Famity I. MYXINIDAG. (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. 
a. Gill openings one on each side, this leading by six ducts to six branchial 
SSE Oe ed Creer hae Sores ven ek ar ae! Ge. 8.0 ae 
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.) 
