CLASS I. MARS1P0BRANCHII. 



The Lampreys. - 



Skeleton cartilaginous; skull not separate from the imperfectly 

 segmented vertebral column; no true jaws; no limbs; no shoulder 

 girdle; no pelvic elements, and no ribs; gills purse-shaped, without 

 gill arches; 6 or more gill openings on each side; nostril single, on 

 top of the head; heart without arterial bulb; alimentary canal 

 straight, simple, without ccecal appendages, pancreas, or spleen; 

 naked, eel-shaped animals. 



Order I. Hyperoartii. 



Nasal duct a blind sac not communicating with the palate; 

 mouth nearly circular, suctorial. 



Family I. Petromyzontitlse. 



The Lampreys. 



Body eel-shaped, somewhat compressed posteriorly; mouth nearly 

 circular, suctorial, and armed with horny, tooth-like tubercles which 

 are simple or multicuspid ; those just above and below the oesophagus 

 more or less specialized ; gill openings 7 on each side of the chest ; lips 

 fringed. 



The lampreys undergo a metamorphosis; the young are toothless, 

 have rudimentary eyes, and live buried in the sand. In the larval 

 state they are white, and evidently feed upon small Crustacea, insect 

 larvae, and the like. In the adult state the lamprey attaches itself 

 to a fish by means of its suctorial mouth, rasps off the flesh, and 

 feasts upon the blood and lymph of the victim. 



1 . Lampetra Gray. 



Lampetra Gray, Proc. Zool. Soc. London, 1851, 235. (Type, Petro- 

 myzon fiuviaiilis Linnaeus.) 



Dorsal fin in two parts, the second part continuous with the low 

 anal fin around the tail; supraoral lamina broad, forming a crescentic 

 plate, with a large, bluntish cusp at each end; lingual teeth small; 

 buccal plate small, its few teeth bicuspid and tricuspid; lips fringed. 

 Lampreys of small size, inhabiting the brooks of Europe and North 

 America. 



