728 PROCEEDINGS OF THE XATIOXAL MUSEUM. vol.xxiii. 



Order HYPEROTRETI. 



THE HA(iFISHES. 



No.stril tube-like, with eartilag-inous rings, penetrating the ])alate, 

 its position at the extremity of the head, over the mouth; snout with 

 eight har})els; mouth without lips; one median tooth on the palate and 

 two comlj-like series of teeth on the tongue. Brantdiial apertures at 

 a great distance from the head; a series of mucous sacs along each 

 side of the abdomen. Intestine without spiral valve. Eggs large, with 

 a horny case provided with threads for adhesion. Marine lamprey- 

 like animals, burrowing into the flesh of fishes, on which they feed. 

 They may be referred to two families, ditfering mainly in the struc- 

 ture of the gill openings, {imspcoa. palate; Tpi/rns, perforate.) 



n. P>ranchial apertures six to fourteen on eaeh side, eaeh leailintr ))y a duet to a 



braneliial sae Eptnlntklx 



an. Braneliial apertures single on each side, from which diverge duets to six bran- 

 (!hial sacs yrii.rinidx 



Family II. EPTATRETID.E. ^ 



This family differs from the 2[i/.rl)il<J(e chiefly in the structui-e of 

 the ))ranchial apparatus, there ])eing six to fourteen sacs on each side 

 which receive Avater directly from the esophagus, as in My.ilne^ but 

 the emptying ducts, instead of passing backward and downAvard to a 

 common external opening, as in Mi/.rhie, pass directly through the 

 Avail of the body, so that there are as many external openings as there 

 are gill sacs. Species few, inhabiting the colder parts of the Pacific, 

 their habits similar to those of My.rl)}e <jh(trno.'«i. 



The hagfish fastens itself usually on the gills or isthnuis of large 

 fishes, sometimes on the eyes, whence it works its AAay Aery rapidly 

 into the inside of the body. It then devours all the llesh of the l)ody 

 Avithout breaking the skin, so that the fish is left a living hulk of 

 head, skin, and bones. It is especially destructive to fishes taken in 

 gill nets. In gill nets, in summer, these empty shells of fishes arc 

 often obtained. When these are taken from the AAater. the hagfish 

 scrambles out Avith great alacrity. It is thought that the hags enter 

 the fishes after they are caught. A fish of 1(» to 1.5 pounds weight 

 Avill l)e devoured bA' them in a single night. 

 (t. Gill openings six to eight on each side Eptalretu.s, 2 



' We adopt the name Eptatretns instead of Homea in deference to the argument of 



Professor (iill in the following ])aper. 



I 



