2. MYXINID.^: BDELLOSTOMA. 
5 
tail representing the spinal column. Month round, suctorial, without 
lips, with a jjair of barbels on each side. Xostril single, large, on 
the median line above, and at the very front of the head, provided 
with two pairs of barbels. Teeth strong, a single median one on the 
roof of the month, and two rows on each side of the tongue, which is a 
powerful organ, with a strong fibrous tendon moving in a muscular 
sheath. Alimentary canal a simi>le, nearly straight tube. Gill-sacs 
placed on each side of the oesoi)hagns, lying directly against its outer 
walls. The water passes into them by a small pore opening directly 
from the cesophagiis into each sac. It is then i^assed out by a duct, 
which continues backward along the outer walls of the sacs to the 
abdominal wall at the end of the last sac, where all the ducts from one 
side unite in one, and the water is emptied at the branchial opening on 
each side of the median line. In close connection with the branchial 
opening on the left side there is a third opening that leads by a very 
short duct to the cesophagns, and hence into the branchial sacs, at 
times when the supply through the mouth is cut oft* by the head being 
buried in the food of the animal. Ovary single, on the right side. No 
oviducts ; the mature eggs falling into the abdominal cavity are excluded 
through the peritoneal oi)eniug at the side of the vent. — {Putnam.) 
A single species; colorless, parasitic animals, burrowing into the 
bodies of fishes, and found in all temperate seas. slime.) 
2. gSaiJifiJOSa L. — Hag-fish; Borer; SJeepmarhen. 
Blue above, whitish below; head 3.1 to 4 in total length; tail 6.J to 10 
times in total length; lingual teeth 8 to 11 in each row {Putnam). 
Coasts of Eiiroi)e and America; not abundant on our shores. 
(L. Syst. Natur® ; Giiutlier, viii, 510 ; Putnam, Proc. Bust. Soc. Nat. Hist. 1873, 135 : 
Mijxine limosa Girard, Proc. Ac. Nat. Sci. Pliila. 1858, 223.) 
3.— I5DEI.I.OSTOMA Muller, 1834. 
(Miiller, Abhandl. Akad. Wiss. Wien, 1834,79: type Petromyzon cirrJiatiis Forster.) 
This genus difiers from Myxine chiefly in the structure of the bran- 
chial apparatus, there being six or more sacs on each side which receive 
water directly from the oesophagus as in 2Iyxine^ but the emptying 
ducts, instead of passing backward and downward to^ a common exter- 
nal opening, as in Myxine., pass directly through the wall of the body, 
so that there are as many external openings as there are gill-sacs. M arm 
seas. (.Sde/lAo!:, leech ; azopa, mouth.) 
