CHAPTER XXI. 



Class CYCLOSTOMATA. 

 {Synonym, Marsipoeranchii.) 



The hag (Myxine), the lamprey (Petromyzon), and a few 

 others like them, differ in so many ways from Fishes, that 

 they must be ranked in a distinct class. They represent an 

 archaic type, whose interest has been enhanced by the 

 discovery of Palceospondylus in the Old Red Sandstone. 



General Characters. 



Unlike all higher Vertebrates ( Gnathostomata), the 

 Cyclostomata have rowid suctorial mouths, without distinctly 

 developed jaws. They are also without paired fins and 

 without scales. Their respiratory system consists of paired 

 gill-pouches, to which the term Marsipobranch refers. In the 

 extant forms the skeleton is wholly cartilaginous, and the 

 notochord persists unconstricted. The " nostril" is unpaired, 

 there is no sympathetic nervous system, no conus arteriosus, no 

 distinct pancreas, no spleen, no genital ducts, and the segmental 

 duct is unsplit. Their geographical distribution is wide. 



First Type. Myxine— The Hag. 



The glutinous hag (Myxine glutinosa) is not uncommon 

 off the coasts of Britain and Scandinavia, the Atlantic 

 coast of America, etc. It lives in the mud at depths of 

 40 to 300 fathoms. It often lies buried with only the 

 nostril protruding from the mud, but it can swim gracefully 

 and rapidly in eel-like fashion in search of prey. It eats 



