1914-] F- H. Gravely : An Account of the Oriental Passalidae. i8g 



metasternum. This is also the case in all genera of the second section of the family, 

 in almost all members of which the indistinct transverse band between the coxae 

 is replaced by a distinct suture. This plate is therefore of some interest in connec- 

 tion with the classification of the family ; but I have not found it possible to utilize 

 it for differentiating species. 



Metathofax. 



The metathoracic episterna and epimeva do not appear to present any charac- 

 ters of taxonomic importance; but the metasternum, which covers the whole of the 

 ventral surface of this segment of the body, must be considered in some detail. Four 

 different regions can easily be recognized in this plate. Firstly, there is a large 

 flattened circular central area, whose boundaries are as a rule less clearly defined in the 

 Aulacocyclinae than in the remaining sub-families. This area is almost always smooth; 

 but in a few species of Leptaulacinae it is rough and may bear strong punctures, 

 very variable in number, whose presence is apparently a constant feature of all the 

 species in which they are found except one, that one being the most variable species 

 of Passalid known to me. The central area is also marked, not infrequently, with ill- 

 defined but symmetrically arranged grooves and depressions, to which taxonomic 

 importance has sometimes been attached. But I have found these much too variable 

 to be of any use. There is, however, in many species of the genera Tiberioides, 

 Episphenus and Leptaulax, a very persistent and strongly marked roughened depression 

 in the middle-line, just behind the anterior margin, to which special attention may be 

 drawn. It s rarely entirely absent in species in which it is ever distinct, and never 

 very distinct in species in which it is normally absent. 



The metasternum is usually bordered on either side by a pair of depressed lateral 

 areas. These may either be of equal width throughout or broader behind than in front, 

 and différences both in width and in shape are usually found to be extremely constant 

 within the limits of each species. The surface of these areas is always roughened or 

 punctured. Between bhe central and lateral areas are the intermediate areas , "which 

 are divided into an anterior and posterior part, more or less completely according to 

 the size of the areas on either side of them. Differences in the extent and nature of 

 the puncturing of the posterior, and to a less extent also of the anterior, interme- 

 diate areas, afford useful confirmatory characters, but usually vary too much within 

 the limits of a single species to be diagnostic by themselves. 



Abdominal sterna. 

 On either side of each abdominal sternum a more or less distinctly triangular 

 depression is often found. These depressions, which we may term scars, are less 

 persistently found in the posterior sterna than in the anterior ones, and in the Aula- 

 cocylinae than in the other subfamilies. They are too variable in shape and distinct- 

 ness to be of use in the differentiation of one species from another ; and I have been 

 unable to find anything connected with the abdominal sterna, except puncturing, 

 which has any taxonomic value — such other characters as have been made use of 

 have proved either to be variable in themselves, or to be dependent on the extent 



