1904.] NATURAL SCIENCES OF PHILADELPHIA. 261 DESCRIPTIONS OF NORTH AMERICAN ARANEiE OF THE FAMILIES LYCOSID^ AND PISAURID^:.! ' BY THOMAS H. MONTGOMERY, JR. A very considerable number of species of spiders of the families Lycosidffi and Pisam-ida? have been described from North America, but for the most the descriptions have barely diagnostic worth. At the present time it is practically impossible to identify most of the species of Walckenaer, Blackwall, Hentz and some others, because some of their species are so insufficiently described that a particular description applies equally well to a number of species. By far the most thorough work so far is that of KeyserHng. When the American species are better known than they are at present we shall be in better position to identify the species named by the earlier writers, for then the identification can be done by the process of ehmination. The more deeply one enters into the closely intergrading species of the Lycosidai especially, the more doubtful seems to be the character of attempts to recognize poorly described forms. Nearly the whole southeastern section of the United States and the greater part of the region west of the Mississippi river have been untouched by modern arachnologists; with such a hiatus in the material for comparison, it would be unscientific to make sure of the status of species known only by inadequate diagnoses. It is right to attempt, as far as possible, to recognize the species of earlier writers, but not to uphold names when the type specimens are lost and when the type descriptions are not decisive. When all the species are known, the trial can be undertaken of determining the earlier species. The Lycosidffi and Pisauridffi are particularly interesting groups because of the difficulties in the way of their study. Not only do the species intergrade closely, but there is very considerable individual variation apart from geographical variation, and the genera are as difficult to define sharply as are the species. No groups are better adapted to prove the idea that the species, as the higher groups, are but concepts, and their dehmitation necessary purely for purposes of de-T^tributions from the Zoological Laboratory of the University of Texas, No. .57.