416 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 104 



species always have the front of the head distinctly granulate or 

 verrucose, the granules rarely more than twice as long as wide, the 

 clypeus emarginate, the pronotum usually fimbriate or ciliate at sides 

 and base, the pygidium grooved basally to receive the ventrally 

 dentate apices of the elytra, the hind spurs and tarsus placed in a 

 straight line rather than in the triangular placing as in Aphodius, the 

 apical fimbriae of the hind tibiae very short and well inside the margin, 

 the external angle of the posterior tibia only very rarely forming a 

 spine, and the first segment of the hind tarsus subequal to or shorter 

 than the long spur. In addition, the pronotum frequently exhibits 

 alternate transverse swellings and punctate furrows or grooves, the 

 hind femurs are usually heavier and wider than the middle femurs, the 

 middle and hind tibiae are usually noticeably widened apically, the 

 tibiae usually without the oblique ridges found in Aphodius but with 

 lengthwise series of setigerous tubercles and sometimes an ante apical 

 carina paralleling the apical margin (species of the Pacific Coast of 

 the United States), and the tarsal segments are nearly always dis- 

 tinctly widened apically and more or less triangular. 



Over half of the American species of Psammodius have the maxillary 

 galea provided with heavy chitinous teeth and the median, more 

 heavnly chitinized area of the epipharynx not extending to the thin 

 membranous anterior edge, as found in the type of the genus, Psam- 

 modius sulcicollis (lUiger) . In the remaining species the galea of the 

 maxilla is covered with close parallel rows of mixed fine, hairlike, and 

 heavy hooked setae, giving a brushlike tip, while the epipharynx has 

 the more heavily chitinized area extended beyond the membranous 

 anterior edge by one or two heavy setae or teeth, exactly as in the 

 genus Ataenius. 



Nearly all species having maxUlary teeth also exhibit transverse 

 pronotal furrows, wide hind femurs, short tarsi, and a strongly convex 

 oval habitus. Those without maxillary teeth usually lack the pro- 

 notal furrows (the pronotum being more or less evenly punctate), 

 show little disparity in the size of the middle and hind femurs, and 

 usually are more elongate in habitus. Unfortunately several species, 

 notably the new species formosus, Jimbriatus, and martinezi, were 

 found to have maxillary teeth combined with external characters of 

 the second group. Because of this and the variation in the develop- 

 ment of external characters it seems unwise to attempt a division of 

 the species into subgenera. 



It is interesting to note that the species bidens, integer, aenictus, 

 atopus, and others all have affinities in the direction of Ataenius, 

 while in Ataenius, the species schwarzi (Linell) and puncticollis 

 LeConte show characters similar to this group of Psammodius. 

 Ataenius and Psammodius probably should be placed in the same 

 tribe of the Aphodiinae. 



