242 COLEOPTERA OF NORTH AMERICA. 



The sexual characters are often wanting, when present will 

 be found in the form of the tibial spurs of the front and middle 

 legs. In one set of species of Aphodius the first joint of the 

 posterior tarsus % is curiously hooked. 



The following genera occur in our fauna : — 



Mandibles concealed beneath the clypeus. 2. 



Mandibles visible beyond the clypeus. Aegialia. 



2. Hind tarsi with elongate, usually cylindrical joints. 3. 

 Hind tarsi with triangular joints. Psammodius. 



3. Head roughly granulate, or verrucose ; prothorax transversely 



grooved. "i- 



Head punctured or slightly plicate. 5. 



4. Prothorax not fimbriate, grooves short, lateral. Pleurophorus. 

 Prothorax with scale-like marginal hairs, grooves entire. 



Rhyssemus. 



5. Protliorax never broader than elytra. l>. 

 Prothorax at base broader than elytra, hind tibise with apical angle 



spiniform. Euparia. 



6. Outer apical angle of hind tibise obtuse. 7. 

 Outer ajjical angle of hind tibiae prolonged spiniform. Ataenius. 



7. Front tibise strongly toothed on the outer margin. S. 

 Front tibias with upper teeth obsolete, terminal tooth anterior. 



Dialytes. 



8. Elytra with costiform interspaces. Oxyomus. 

 Elytra simply striate. Aphodius. 



The species formerly placed in Euparia, with the exception of 

 castanea, belong to Ata^nius. 



Tribe III.— ORPHi\I\I. 



Oval, convex species, of brown color, covered above with short 

 erect hair; the elytra arc striate; the mandibles and labrum are 

 corneous, not covered by the clypeus, which is not dilated as in 

 the two preceding triljes; antenna3 10-jointed, club 3-jointed, some- 

 what rounded; anterior coxa^ prominent; middle coxa? oblique, 

 contiguous; epimeraof the metathorax covered; ventral segments 

 six, jiot connate; tarsi with a small setigerous onychium. 



Our species are moderately numerous, and are found from the 

 Mississippi westward to Arizona and Nevada, and are nocturnal 

 in liabits, being attracted by lamps. Ochodasus is distinguished 

 from the other genera of the tribe by the eyes being not emargi- 

 nate. The method of life is unknown. 



