404 Wisco7hsin Academy of Sciences, Arts, and Letters. 



ANALYTICAL KEY TO THK iS'OltTK AMERICAN SPECIES OF DIAPTO- 

 MUS BASED ON THE CHABACTEES OF THE A£AJLB. 



Antepenultimate segment of the male right antenna with- 

 out a diotok' t appendage, 

 Antepenultimate segment slightly produced at the 

 distal end into a blunt point, first segment of 

 right exopodite with marked quadrangular hy- 

 aline appendage, Birffei »- c 



Right and left feet nearly equal in length, terminal 



hook of right foot symmetrical, oregonensis - P 



Xieft foot shorter than right, 

 , Left foot reaching beyond first segment of the ex- 

 opjodite. 

 Terminal hook of right foot uniangular, right 

 endopodite equal in length to first segment 



of the exopodite Reighardi — P 



, Terminal hook biangular, right endopodite large, 

 ' longer than first segment of the exopo- 

 dite, mississippiensis - f>> 



Left foot reaching end of first segment of the 

 exopodite. 



Inner process of the terminal segment of the 

 left exopodite falciform, no hyaline append- 

 age of first segment of right exopodite pallidiis - f>' 



Inner process of terminal segment of left ex- 

 opodite digitiform, a hyaline appendage on 

 internal distal angle of first segment of 



right exopodite Tyrelli * p- 



Antepenultimate segment of male right antenna with 



hyaline lamella. 



Hyaline lamella broad, extending beyond the end of 



the segment, secoTid basal segment of the right 



exopodite armed on the posterior surface with a 



small hook, leptopus - 



Hyaline lamella narrow, extending beyond the end of 

 the segment slightly, if at all, first basal segment 

 armed with a hook equal in length to the first 



segment of the exopodite, clavipes - P 



.Antepenultimate segment of the right antenna bears 

 a slender straight process. 

 This process is much shorter than the penultimate 

 segment. 

 Right endopodite rudimentary. 



Lateral spine of the second segment of the right 



exopodite is terminal Lintoni - P 



Lateral spine of the second segment of the ex- 



