Classification (f Tcleostean Fishes. 77 



B. Vertehral centra complete, annular or biconcave ; no separate 



pleuro-ceutra and hypo-centra .... 2. Aaindorhynchii. 



C. Vertebral centra complete, opistbocoelous ; no separate pleiiro- 



centra and bypo-centra 3. G'mylymodi. 



II. No splenial ; an endocbondral supraoccipital ; vertebral centra 

 complete. 



A. A mesocoracoid f. 



1, No VVeberian ossicles; maxillary entering thegnpe to a greater 



or less extent and not acting as a lever for the protraction of 

 the prsemaxillaries; mesetbmoid unpaired. 



4. Isospondyli. 

 a. Frontals united by suture. 

 «. Moutli not protractile. 



* Parapopbyses autogenous or parietals separated by 

 supraoccipital. 



Parietals present 4 o. Clupeoidei. 



I'arietals absent 4 6. Stomiatoidei. 



** Parapophysesco-ossified with centra; parietals meeting, 

 separating frontals from supraoccipital. 

 Entopterygoid articulating with a lateral peg 



of the paraspbenoid 4 c, Osteoglossoidei. 



On eacli side of the skull a lateral foramen or 

 cartilaginous area superiorly and a vesi- 

 cular diverticulum of the air-bladder 



inferiorly 4 f/. Notopteroidei. 



On each side of the skull superiorly a lateral 

 foramen lodging a vesicle '\sdiicb bas lost 

 its connection witb the air-bladder .... 4 e. Mormyroidei. 



{i. Moutb protractile; maxillaries not articulated to the 

 cranium 4y, Pbractolsemoidei, 



h. Frontals united to form a single bone ; gill-membranes 

 joined to the isthmus 4,^/. Oonorhynchoidei. 



c. Frontals completely separated ; gill-menibranes joined to 

 the isthmus 4 /«. Cromerioidei. 



2. Weberian ossicles present 5. Ostariopliysi. 



Parietals distinct ; pterygoids, symplectic 



and opercular bones all present ; anterior 



vertebrae more or less distinct 5 «. C\prinoidei. 



Parietals united with supraoccipital ; no 

 metapterj'goid, symplectic, or suboper- 

 culum ; anterior vertebrae co-ossified . , bb. Siluroidei. 



B. No mesocoracoid. 



]. Parapopbyses autogenous. 



a. Parietals united by suture ; mesethmoid unpaired ; physo- 



clistic 6. Heteromi. 



b. Parietals separated by the supraoccipital ; paired dermal 



ethmoids ; phj'sostomous .... 7. Haplotni. 



Pectoral pterygials normal 7 «. Esocoidei. 



Pectoral pterygials represented by a cartila- 

 ginous plate 7 b. Dallioidei. 



t Absent in some ArgentinidtB and Silurida; and in the Galaxiidte 

 and Ilaplochitonidte. 



