CLASS It, OKBER 



ORDER 6. eHONDROPTERYGIOUS, 



Skeleton cartilaginous? without ribs ; gill-mem- 

 Ijranes wanting, with or without gill-covers. 



PETROMYZO:N, (lamprey,) body eel-form ; mouth 

 beneath, with numerous teeth in circular rows : 

 spiracles seven on each side the neck. 



GTASTROBRANCHUS, (hag-fish,) hody eel-form^ 

 mouth beneath, with numerous pectinate teeth : 

 spiracles two, beneath the abdomen. 



RAJA, (ray,) mouth situated beneath the head, 

 transverse, beset with teeth ; spiracles beneath, 

 iive on each side of the neck ; body, in most spe- 

 cies, subrhomboidal. 



SQUALUS, (shark,) mouth situated beneath the 

 anterior part of the head, with numerous teeth dis- 

 posed in rows ; spiracles on each side the neck 

 (inmost species five,) of a semi-lunar shape ; body 

 oblong, somewhat cylindric. 



SPATULAIUA, habit as Squalus, ; spiracles sin- 

 gle on each side the neck and concealed by a large 

 gill-cover ; snout produced, spatulate ; mouth be- 

 neath the head, large and furnished with sharp 

 serrate teeth. 



Acii'ENCER, (sturgeon, sterlet,) having gill- 

 covers ; snout bearded beneath : mouth beneath 

 the head, ovate, toothless, retractile ; body elon- 

 gated, mailed above by tubercles. 



PEGASUS, having gill-covers ; snout elonged 

 not bearded ; mouth beneath ; pectoral fins large ; 

 ventral fins single-rayed ; body depressed, mail- 

 ed,, with the abdomen divided into bony segments* 



