1 lámina, The Pyrgmorphidae are divisible into 30 tribes on the basis of their external morphology, phallic and concealed female structures — some change from the previous arrangement of these tribes is proposed. A linear sequence is difficult to devise because of the lack of correIation in the different tribes between 'primitive and `derived' characters. The tribes are placed in two arbitrary groups, A and B, based largely on the form and disposition of the metasternal pits. Within Group A, four, 'and 'within Group B, six series of tribes are recognized. The present work deals in detail only with Series I and II of Group A, but all series and tribes are usted, together with notes on recent changes. For each tribe of Series I and II, the full tribal synonymy, a definition, with particular reference to the phallic and concealed female structures, and all included genera and species 'with their general geographic distributions are given. The phallic and concealed female structures of a representative of each genus are illustrated in detail (except for genera in .which only one sex is known). Some discussion of tribal relationships is included where appropriate.