444 WILLIAM K. GREGORY 



a division recently suggested by Professor Osborn to express 

 the relations of Marsupials to Placentals which together consti- 

 tute the subclass Eutheria Gill (not of Huxley) in contrast to the 

 subclass Monotremata. The differences between Marsupials 

 and Placentals do not seem to be more deep-seated than the 

 differences between the Crossopterygii on the one hand and the 

 Actinopteri Cope (all the remaining Ganoids and Teleosts), 

 on the other. Hence I regard the Crossopterygii and Actinopteri 

 as infraclasses. Again the Dipnoi show many resemblances 

 to the Crossopterygii in their comparative anatomy, embryol- 

 ogy, and palaeontology, and it seems advisable to express this 

 relationship by ranking the Dipnoi as an infraclass, coordinate 

 with the Crossopterygii and Actinopteri, the three groups being 

 embraced within the subclass Teleostomi, a procedure already 

 suggested in essentials by Gill. 1 After the exclusion of Polyp- 

 terus and its allies from the Ganoidei, this classic term with its 

 congeneric term Teleostei may be used in a perfectly clear sense 

 as by Jordan and Evermann, for the upper and lower divi- 

 sions of the Actinopteri. These divisions we may call cohorts, 

 the cohort having been used by Storr in 1780 in the classifica- 

 tion of the Mammals. The cohort Ganoidei may be taken to in- 

 clude the superorders Acipenseroidei Traquair, Lepidosteoidei (as 

 understood by Bridge in The Cambridge Nat. Hist., vol. " Fishes," 

 etc.) ; the cohort Teleostei to include the superorders Mala- 

 copteroidei (embracing the orders Isospondyli, Ostariophysi) , 

 Mesichthyes (Hay) (embracing the orders Haplomi, Synentog- 

 nathi, Salmopercag) , Thoracostraci Swinnerton (embracing the 

 orders Hemibranchii, Lophobranchii) , Acanthopteroidei (em- 

 bracing the orders Percesoces, Anacanthini, Labyrinthici (?), 

 Acanthopterygii, Selenichthyes, Taeniosomi, Plectognathi, Hypo- 

 stomides, Opisthomi, Pediculati). The superordinal relationships 

 of the eel-like orders Apodes, Symbranchii, Heteromi, whether 

 to the Ganoid, Malacopteroidei, or Mesichthyes are not clear. 



It will be seen that the classification given herewith adheres 

 to the American standard in regarding as orders such great groups 

 as the Ostariophysi, the Acanthopterygii proper, the Haplomi, 



» "Addresses in Memory of Edward Drinker Cope." Proc. Amer. Philos. 

 Soc, Memorial Vol. I, 1900, pp. 15, 16. 



