34 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 123 



in the Mountain Lake region, the triunguis females of the four species 

 of the genus Dactylocythere may be recognized by the presence of an 

 amiculum (figs. 7e, h-k) and the posteroventral projection on the 

 shell of Dt. daphnioides (fig. If), Donnaldsoncythere by the small 

 corneous tubercles in the posterodorsal portion of the body, Ascetocy- 

 there by the small rounded prominence partially surrounded by an 

 amorphous mass of refractile material in a corresponding position 

 (fig. 7c), and Entocythere by the pectinate projection at the base of 

 the terminal claws of the second antenna (fig. 7b). 



Key to Male Ostracods 



1 Copulatory complex provided with finger guard 2 



1' Copulatory complex lacking finger guard 6 



2(1) Peniferum without accessory groove; peniferum bulbiform distally. 



Phymocythere phyma 



2' Peniferum with accessory groove; peniferum variable but never bulbiform. 



Dactylocythere ... 3 



3(2') Accessory groove extending distinctly dorsal to spermatic loop. 



Dt. falcata 



3' Accessory groove extending approximately to dorsal level of spermatic 

 loop • 4 



4(3) Posteroventral margin of shell with conspicuous prominence. 



Dt. daphnioides 



4' Posteroventral margin of shell without conspicuous prominence . . 5 



5(4') Junction of horizontal and vertical rami of clasping apparatus con- 

 spicuously thickened, and horizontal ramus provided with prominent 

 tooth near junction Dt. chalaza 



5' Junction of horizontal and vertical rami of clasping apparatus not con- 

 spicuously thickened and horizontal ramus not provided with prominent 

 tooth near junction. Dt. suteri 



6(1') Distal portion of peniferum with prominent flange and finger-like pro- 

 jection Ascetocythere asceta 



6' Distal portion of peniferum never with prominent flange or finger-like 

 projection 7 



7(6') External border of horizontal ramus of clasping apparatus with long 

 talon Ankylocythere ancyl a 



7' External border of horizontal ramus of clasping apparatus entire . . 8 



8(7') Horizontal and vertical rami of clasping apparatus distinct and forming 

 right angle; internal border of horizontal ramus serrate along entire 

 margin Entocythere ... 9 



8' Horizontal and vertical rami of clasping apparatus not distinct and 



joining in angle greater than right angle; internal border of horizontal 

 ramus never with more than three teeth. 



Donnaldsoncythere ... 10 



9(8') Mesial surface of junction of horizontal and vertical rami of clasping 

 apparatus thickened and armed with one or more teeth or ridges. 



E. internotalus 



9' Mesial surface of junction of horizontal and vertical rami of clasping 



apparatus not thickened and without teeth or ridges. 



E. kanawhaensis 



