j'KTiio.MYZONTrnj;. 490 



Subclass V. CYCLOSTOMATA. 



kSkeleton cartilaginous and notochorclal, without 

 ribs, and without real jaws. 8kull not separate from 

 the vertebral column. No limbs. Gills in the form 

 of fixed sacs, without branchial arches, six or seven in 

 number on each side. One nasal aperture only. 

 Heart without bulbus arteriosus. Mouth anterior, 

 surrounded by a circular or subcircular lip, suctorial. 

 Alimentary canal straight, simple, without ca3cal aj)- 

 pendages, pancreas, or spleen. Generative outlet pe- 

 ritoneal. Vertical fins rayed. 



Cfr. Miillcr, Abbaudl. Ak. Wiss. Berlin, 1834, p. 7(5. — These fishes 

 were ]iamed Marsiiiobruncliii by Uoiiapartc, and form one of the 

 two suborders of the Subchiss iJcrmopteri of Owen (Anut. Yert. i. 

 p. 7). Midler has divided them into two families : — 



I. PetromyzontidaB. The nasal duet terminates blind, not i)ene- 

 trating the palate (p. 41)0). 



II. Myxinidae. The nasal duct jienet rates the palate (p. r)J()). 



Fam. 1. PETROMYZONTIDiE. 



Cyclostomata hyperoartia, MnUcr, AhhmuU. Ak. Wixs. Bcrl. 1834, 

 p. 77. 



Body eel-shaped, naked. Subject to a metamor- 

 phosis. In the perfect stage with a suctorial mouth 

 armed with teeth simple or multicuspid, horny, sitting 

 on a soft papilla. Maxillary, mandibulary, lingunl, 

 and suctorial teeth may be clistinguislied. Eyes pre- 

 sent (in mature animals). External njisal apc^-fnro in 



