2 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



Although no representatives of the class have been found in a fossil condition, their 

 absence in the older strata is undoubtedly due rather to the difficulty connected with the 

 preservation of the readily destructible cartilaginous skeleton than to their actual absence. 

 It is indeed probable that the order was extensively represented in past times and that it 

 was more abundautly developed than any other type. (Gill.) 



Order HYPEROTRETA. 



Cyelostomata hyperotreta, Mcller, Abhandl. Akad. Wiss. 

 Hyperotreta. Gill, .lohnson's Cyclopaedia, n, 1079. 



An order of marsipobranchiates characterized by the construction of the cranial carti- 

 lages and the complete tabulation of the median nasal aperture, and its perforation of the 

 palate (hence the name). The branchial apertures are developed on each side far behind 

 the head, and arc variable in number: the inner branchial ducts communicate directly 

 with the esophagus; the ova arc large and each is provided with an oval horny case con- 

 stricted at both ends, and with numerous filaments thereto. The embryology is still unknown. 

 In the adult condition the mouth has no lips and no plates on the disk, but a median tooth 

 is above the entrance of the esophagus, and two pectinifonn rows of teeth on the tongue. 



The order is composed of two families: (1) Myxinidce, with one geuus, Myxine, repre- 

 sented by species in the northern and southern hemispheres; and (2) Bdellostomidce, whose 

 species are confined to the Pacific Ocean, one of them ascending as far northward as Cali- 

 fornia. (Gill.) 



Family MYXINIDCE. 



Afyxinidce, GCxther, Cat. Fish. Brit. Mus., vm, 1870, 510. 



MYXINE, Linnseus. 



Myxine, I. inn i:cs, System:! Naturae, ed. x, 1. 1758, 650 I type, Myxine glutinosa, L.). 



Body eel shaped, covered by a thin loose skin ; two rows of mucous glands along the 

 lower side. Eyes absent. Skull little developed, cartilaginous. Mouth lipless, suctorial, 

 with barbels on each side. Nostril single, median, at front of head, with two pairs of 

 barbels. Teeth strong, a single one on the roof of the mouth, and two rows on each side 

 uf the tongue. < 4 ill sacs at the sides of esophagus near the left branchial opening; a third 

 opening to esophagus and the branchial sacs. Ovary single, on right side. No oviducts. 



MYXINE GLCTINoSA, Lixx.s:is. (Figure 1.) 

 Myxine glutinosa, Linn., Syst. Nat., ed. x. i. 65 i; ed. xn, 1080. — Gunther, Cat. Fish. Brit. Mus., vm. 510. 



A Myxine with 8-11 rather slender lingual teeth in each row, the two foremost strongest 

 and more confluent at the base thau the others. Length of head contained 3i to 4 times in 

 total length ; tail 6 J to 10 times. Color grayish brown to bluish brown above, whitish below. 



Linmvus included Myxine among his '• Vermes Intestinal placing it between the leeches 

 and the shipworms, and described its habits briefly as follows: "IntreU etdevorat pisces; 

 aquam in gluten mutat," and this sentence expresses nearly all that is known about the 

 habits of the animal at the present time. It may be said, however, that it is found only in 

 waters of low temperature, probably always below 50°, and that on account of its parasitic 

 habits its capture is not likely to be effected except in connection with some larger fish on 

 which it is preying. Its presence, therefore, is not certain to be detected by the trawl and 

 dredge. The "slime-eel," as it is called, frequently penetrates into the abdominal cavity of 

 other fishes to feed upon their flesh. It secretes thick, glutinous slime, in enormous quan- 



