While accumulating material for a long needed review of nearctic megalomorph spiders, a considerable number of species in the family Aviculariidae have been noted which it seems desirable to diagnose and name at this time. It is the purpose of the present paper to do this.
It has been found convenient for the present to recognize and use the genera indicated in the key given below, although the limitation of some of these groups, e.g., Dugesiella and Aphonopelma, is not yet as precise as might be wished for. Of these genera Aplionopelma embraces the great majority of the species of the United States falling in the old group Eurypelm a as used by Simon.
For loan of material in connection with the present study special acknowledgment is due to Clinton G. Abbott, Director of the Natural History Museum at San Diego, Dr. W . J. Gertsch of the American Museum of Natural History, Dr. A. I. Ortenburger of the University of Oklahoma, Dr. L. T. Murray of Baylor University, and Prof. J. C. Cross of the Texas College of Arts and Industries.