CRUSTACEA OF ALABAMA. 23 



the male, but much shorter in the female. The adult male was not seen. This species 

 approaches C. minnesotensis in several respects and is about .50 mm. long. 



ORDER OSTRACODA. 



In some respects the structure of the animals of this order is very primitive and it 

 has been thought that the order was one of the earliest branches to separate from the 

 crustacean stem. Conformably to this theory the remains of Ostracoda are found in 

 rocks of the earliest fossiliferous periods. These animals are especially adapted for such 

 preservation since the compact and unsegmental body is enclosed in a more or less in- 

 durated limy or chitinous bivalved shell. The shell is closed by adductor muscles and 

 opened by a ligment as in mollusks and consequently these animals are often mistaken 

 for minute shell-fish. The abundance of the fossils of this group makes them a valuable 

 geological criterion and accordingly they are now receiving much more attention than 

 formerly. At the foundation of such study, however, must lie a familiarity with existing 

 species, an accomplishment possessed by very few zoologists not to say geologists. 

 The majority of the species are marine, but three or four genera and numerous species 

 inhabit our fresh-water. The writer has long entertained the hope of adding something 

 substantial to the knowledge of the American species, but being reluctantly obliged to 

 relinquish the hope feels bound to place the few incomplete notes collected at the dis- 

 posal of others. A month's systematic study of our fauna in a favorable locality would 

 double the number of species here mentioned. It is not unlikely that the modern 

 Branchiopoda and Cladocera, had their origin as off-shoots of this group either independ- 

 ently or, more probably, the latter meditated by the former. A gradual progression is 

 seen in the Ostracoda from a nauplius-like creature to a highly complex organism with 

 lamellar post abdomen and bi-ramose second antennae similar to certain Cladocera. The 

 order may be divided into two groups in one of which the second antennae are simple, in 

 the other biramose. The latter includes the suborders Myodocopa, Cladocopa, and Pla- 

 tycopa, all marine, while the former constitutes the suborder Podocopa containing the 

 families Cypridae, Darwinellidae and Cytheridae, with the first of which alone we are at 

 present concerned. 



FAMILY CYPRID.E. 



Anterior antennae simple, adapted for swimming, setose; second antennae sub-pedi- 

 form, clawed ; mandibles toothed, palpate ; first maxillae with a branchial plate, second 

 with or without branchial plate ; feet of two pairs, first directed forward, clawed, second 

 turned backward and upward, feebly armed ; abdomen ending in narrow rami, clawed, or 

 spined apically, sometimes nearly rudimentary. About ten genera are known, of which 

 four are found in fresh-water, and but one of which occurs in the fresh waters of America, 



