2. MYXINID^E BDELLOSTOMA. 5 



tail representing the spinal column. Mouth round, suctorial, without 

 lips, with a pair of barbels on each side. Nostril 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 mouth, 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 simple, nearly straight tube. Gill-sacs 

 placed on each side of the oesophagus, lying directly against its outer 

 walls. The water passes into them by a small pore opening directly 

 from the oesophagus into each sac. It is then passed out by a duct, 

 which continues backward along the outer walls of the sacs to the 

 abdominal Avail 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 oesophagus, and hence into the branchial sacs, at 

 times when the supply through the mouth is cut off 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 opening 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. (;j.o^a, slime.) 



2. OT. gflutifliosa. L. Hag-fish; Sorer; Sleepmarken. 



Blue above, whitish below ; head 3 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 Europe and America; not abundant on our shores. 



(L. Syst. Naturae ; Gtiiitlier, viii, 510 ; Putnam, Proc. Bost. Soc. Nat. Hist. 1873, 135 : 

 Myxine limosa Girard, Proc. Ac. Nat. Sci. Phila. 1658, 223. ) 



3. BDELLOSTOIHA Mailer, 1834. 

 (Miiller, Abhandl. Akad. "VViss. Wien, 1834, 79 : type Petromyzon cirrhatus Forster.) 



This genus differs 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 Myxine, 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. Warm 

 seas. (p3M<>S) leech ; or^ua, mouth.) 



