878 THE AMERICAN NATURALIST. (VoL. XXXIII. 
The literature of the Ostracoda is legion, but all known 
American fresh-water forms are described and figured in the 
following publications. The first two also contain a fairly 
complete bibliography up to 1896. 
HERRICK, C. L., and TURNER, C. H. Synopsis of the Entomostraca of 
Minnesota, Copepoda, Cladocera, and Ostracoda. Geol. and Nat. Hist. 
Survey of Minn. 1895 
SHARPE, R. W. Contribution to a Knowledge of the North-American 
Fresh-Water Ostracoda included in the Families Cytherida and Cypridide. 
Bull. Ill. State. Lab. Nat. Hist. Vol. iv. 1897. 
TURNER, C. H. A Male Erfetocypris barbatus Forbes. Zool. Bull. 
Vol. ii, pp. 199-202. 1899. 
In compiling the following key free use has been made, not 
only of my own manuscript notes and published papers, but 
also of the published works of Brady, Vavra, and Sharpe. 
The key includes all fresh-water genera known to me, 
whether they occur in America or not. An attempt is made to 
incorporate all known American species. A few European 
forms not yet found in America are included. All such 
forms are marked with an asterisk (*). 
KEY FOR THE DETERMINATION OF THE AMERICAN FRESH—-WATER 
OSTRACODA. 
A. Second anņntennæ unbranched . >. . . . . `. . PODOCOPA 
AA. Second antennæ two-branched. ; 
B. One branch rudimentary and immobile . . MYODOCOPA* 
BB. Both branches developed. 
C. Basal portion of the first antennæ geniculate, and the 
branches of the second antennæ flattene 
PLATYCOPA* 
CC. Basal portion of the first antenne not geniculate, and the 
branches of the second antennnz not flattened 
CLADOCOPA* 
TRIBE PODOCOPA.! 
A. Last pair of legs bent backwards within the shell and not used for 
locomotion. ... > =: ra rooe e o CYPRDIDA (1) 
1 The marine genera Aglaia, Argillæcia, Anchistrocheles, Cyprois, Paracypris, 
and Pontocypris are not included in this key. 
* Contain no fresh-water forms. 
