48 INVERTEBRATE ZOOLOGY. 



Sub-order 1. Chondrostei Notochord an imsegmented cartilaginous 



rod. upon which the arches and other 

 vertebral elements rest. Integument with 

 rows of bony plates, or naked. 

 ^ Accix>easer, Polyodon. 



Sub-order 2. Holostei Notochord with bony constrictions, cor- 

 responding to the vertebral centra. 

 Skull with membrane bones. 

 ■^ Lepidostens. 



Order 3. Teleostei Skeleton osseous. Scales cycloid or cten- 

 oid. Tail homocercal. Gills provided 

 with an opercuhim. 



Sub-order 1 . Ph ysostoiui Swimming bladder provided with a pneu- 

 matic duct. Ventral fins abdominal. 

 Fin rays soft. Almost all the fresh 

 water fish belong here. -^ Salmo. 



Sub-order 2. Physoclisti Swimming bladder without connection 



with alimentary tract, often wanting. 



Group 1. Anacanthini Fin rays weak. Ventral fins anterior to 



pectoral, if Gadus. 



Group. 2. Acatithopieri Some fin rays spinous, at least of the 



dcirsal fin. Inferior pharyngeal bones 

 separate. The largest group of Teleosts. 

 if Scomher. 



Group II PJia npuiogn a f h i.. ..Sovae fin rays spinous. Inferior pharyn- 

 geal bones separate, if Labrus. 



Group 4. Plectocfiiathi A small group of very compact forms. 



Maxilla and prae-maxilla immovably 

 joined with skull, if Diodon. 



Group •"). Lopltobnuichn Gills tufted, eggs carried by male in a 



brood sack. Body covered by large 

 plates, if Hippocmnpus. 



Class II. Dipnoi • . . . Skeleton mainly cartilaginous. Noto- 

 chord persistent. Paired fins with a cen- 

 tral skeletal axis and with or without 



