no. 1646. REVISION OF BE) RIG II I ID.E—ULRICH AND BA88LER. 279 



include at least one or two of the broadly margined Primitiae. In a 

 later publication ° two other simple Beyrichian genera were intro- 

 duced, namely, Primitiella and Hattietta, both founded on groups of 

 species previously referred to Primitia. In the same work two some- 

 what aberrant Primitian genera, Dilobella and DicraneUa, were also 

 described. 



Except Synaphe, all of these twenty-one genera have turned out 

 to be reasonably natural generic groupings of the species previously, 

 and in most part since, referred to the Beyrichiidae. With the recent 

 multiplication of species through the discovery of new forms, it 

 happens, as might be expected, that many of the species referred to 

 the new genera, in the perhaps pardonable wish to emphasize the im- 

 portance of the latter, now appear to belong to other not less well 

 defined groups whose discrimination seems equally essential in an 

 adequate classification of the wealth of specific forms now known. 

 Because of the small range of diagnostic characters furnished by the 

 shells, and more the inconstancy of these characters when a great 

 group like .Jones's Beyrichiidaj is considered, it is impossible to formu- 

 late a broad family definition without going into undesirable detail. 

 In the classification of living Ostracoda the family groups are based 

 on anatomical modifications, the shells being scarcely considered. In 

 fossil forms, obviously, the systematist is limited to modifications of 

 the carapace. While, the paleontologist's classification is, therefore, 

 liable to grave misassociations, it should be remembered that the 

 results of his efforts may be the best obtainable with the criteria 

 available to him. 



After a considerable study of living Ostracoda, the writers have 

 been forced to the conviction that students of fossil species, especially 

 those found in Paleozoic rocks, can not expect much help in their 

 labors from even an extensive knowledge of living forms. The 

 Cyprida?, even, which family, perhaps on account of lack of diag- 

 nostic characters, is at present thought to range back in time to early 

 Ordovician, may yet be shown to be distinguishable from their pre- 

 sumed Paleozoic representatives. The Leperditiidse and Beyrich- 

 iida\ however, stand alone with no recognized close affinities to post- 

 Paleozoic Ostracoda. These fossils, therefore, the paleontologist 

 must work out for himself and do the best he can with the material 

 at his command. 



After the foregoing introductory remarks, some attempt to re- 

 define the existing classification of Paleozoic Ostracoda is necessary. 

 As the investigations are far from complete, the attempt must, to a 

 considerable extent, be preliminary to the final effort to be made in 



"Geo!, and Nat. Hist. Surv. Minnesota, Final Kept., Ill, Pt. 2, 1894, m>. 

 U2U-693. 



