100 



Day: Ephemeroptera 



posterior and anterior 



Fig. 3:24. a, Tricorythodes sp ?, fore wing; b,c, Tricorythodes sp ., ,*»<»•»■■»■ u,, u ..... 

 lamellae of first nymphal gill; a'.e, Caen/s sp ?, second and first gills of nymph; f, Caenis sp ?, 

 nph; g, Callibaetis sp ?, wings; h, Centroptilum sp ?, wings; /, Call ibaetis californicus, wings 



nymp 



of male; /, Callibaetis pacificus, wings of male; k, Caenis tardata, male genitalia; I, Trichory- 

 thodes explicatus, male genitalia; m, Callibaetis sp ?, fourth gill of nymph; n, Baetis sp ?, third 

 gill of nymph; o, Centroptilum sp ?, first gill of nymph; p, Callibaetis sp ?, male genitalia; q, 

 Callibaetis sp ?, head of male showing divided eyes (a-e,g,h,m-p, Spieth, 1933; r,i-/,q, Needham, 

 Trover, and Hsu, 1935). 



