6 Memoirs of the Indian Museum. [Vol. VII^ 



In order to prevent subsequent confusion I have redescribed, or have at least directed 

 attention to the distinctive characters of, every species that I have seen, excepting only the 

 Oriental ones described in my previous paper ; and I have figured a large proportion 

 of them. This is made essential by the unsatisfactory condition of most of the existing 

 descriptions, a condition which has united with the incompleteness of the collection before 

 me to make the compilation of a satisfactory synonymy of the species very difficult, if not 

 impossible. No attempt has been made to deal with the synonymy of species, the 

 references given being in all cases to original descriptions or to others on which I may have 

 relied in making my determinations. 



The forms dealt with in my " Account of the Oriental Passalidae " naturally receive less 

 detailed treatment than the others. The keys to the determination of genera published in 

 that work are, however, repeated with such alterations as further study has shown to be 

 desirable ; and, except in some of the smaller genera, keys have been given to the identi- 

 fication of all species known to me, although in a few cases these are practically identical 

 with those already published. 



The first serious attempts made to divide the Passalidae up into genera were those of 

 Kaup in 1868-9 and 187 1, respectively. In his " Monographie der Passaliden," published in 

 the latter year, he set forth a remarkable conception of the Animal Kingdom, which led him 

 to postulate a series of subdivisions into co-ordinated series of fives. Believing, as he did, 

 that none of his five sub-families of Passalidae could contain more than five groups, that no 

 group could be composed of more than five genera, and no genus of more than five species, 

 and believing that corresponding species, genera and groups were to be found respectively in 

 all or almost all genera, groups and sub-families, his system of classification inevitably led 

 to a considerable amount of wide separation of closely related genera and species. 



In 1886 Bates introduced a number of changes into Kaup's classification of the American- 

 species. He brought together in one section all those in which the elytra are relatively short, 

 and more or less protuberant in the middle of the base, and into another all the rest; — i.e., 

 those in which the elytra are moderately long with broadly emarginate base — subdividing each 

 of these sections primarily according to the lengths of the antennal lamellae. Unfortunately 

 for this classification the shape of the elytra is correlated with the modification of the wings 

 for stridulation and the loss of the power of flight, changes which not only appear to have 

 taken place in some of the most highly specialized forms of several different American groups, 

 but are also found among widely separated In do- Australian genera (see below, p. 125) ; and 

 the lengths of the antennal lamellae rarely seem, to have much phylogenetic importance, 

 being more or less variable in a number of genera, perhaps in all (see also Gravely, 1914c, 

 pp. 180 and 182). 



Kuwert's elaborate " Passaliden dichotomisch bearbeitet " is still more lacking in any 

 sense of phylogenetic values, and disregards in addition the facts of geographical distribution. 

 Zang and Arrow have done much useful work in the direction of clearing up various items 

 of the confusion thus produced, and my " Account of the Oriental Passalidae " has, I hope, 

 helped to reduce the classification of the forms with which it deals to order ; bat Kuwert's 

 remains the most recent monograph of the Passalidae of the world. In my " Account of the 

 Oriental Passalidae " I have recorded all references known to me relating to Oriental genera 



