732 PROCEEDINGS OF THE NATIONAL MUSEUM. v,,i xxm. 



Order HYPEROARTII. 



THE LA:\rPREYS. 



ISasal duct a l)liiul sac. not ])enetratinif the palate. This order is 

 equivalent to the sing-le family J\ir<nnijz<>niiJ<v. {t)7Tepcoa\ palate: 

 apring^ complete; i. e.. entire.) 



Fiimily IV. PETROMYZONID.E. 



(THE EA:\rPREYS.) 



Body eel-shaped, suhcylindrical anteriorly, compressed behind; the 

 mouth nearly circular, suctorial, usually armed with horny teeth, 

 or tooth-like tul)ercles which are simple or multicuspid resting- on 

 papillii?; those immediately above and those immediately below the 

 oesophagus more or less specialized; eyes developed in the adult: gill 

 openings 7. arranged in a row along the sides of the '* chest:" nostril 

 on top of the head just in front of the eyes; lips present, usually 

 fringed; dorsal tin more or less deeply divided by a notch; the 

 posterior part commonly continuous with the anal around the tail; 

 intestines with a spiral valve; eggs small. 



These animals undergo a metamorphosis; the young are usually 

 toothless and have the eyes rudimentary. Separate generic names 

 {AmmoavtcK, ScolcC(ts(irn((^ CJillnptci'iix) had been applied to these 

 larval forms before it was discovered that they were the normal young 

 of the true lampreys. 



The lampreys inhabit rivers of temperate regions. They attach 

 themselves to fishes and feed ])y scraping oH' the ilesh with their rasp- 

 like teeth. Most of them ascend rivers or brooks at the spawning 

 season, after which very many of the individuals die. 



a. Second dors^al continuous witli caudal. 



''. Snpraoral and infraoral lamin;v with teeth or tooth-hke tubercle;^. 



r. Supraoral lamina very large, expanded laterally, fonning a crescent- 

 Bhaped plate with a cusp at either end and rarely a very small 

 median cusp; anterior lingual tooth little developed, its edge 

 crescent-shaped and dentate, the middle denticle enlarged; buccal 

 disk sniall, the lateral teeth small and never tricuspid; dt»rsal fins 

 separate or united at ]>ase: small lam})reys; fiuviatile. Lampetni, 4. 



4. LAMPETRA Gray. 



Ldiiipefrii Gray, Proc. Zool. Sot-. London. LSol, p. 2oo [HufidUs). 



Lampreys of small size, with the dorsal hn emarginate. or divided 

 into two parts, the posterior portion continuous with the low anal tin 

 aroiuid the tail; supraoral lamina broad, forming a crescentic plate, 

 with a large l)luntish cusp at each end. and rarely a very small 

 median cusp; lingual teeth small, with a crescent-shaped dentate 

 edge, the median denticle enlaroed: buccal disk small, its teeth few 



