SCAItABiEIDAE. 121 



Eyes strongry emarginated by the margin of the head ; 



Labrum subtriangular, rounded in front. Lucanus. 



Labrum very short, broad, truncate, or emarginate. Dokcus. 



Eyes almost entire ; sixth ventral segment visible. Platycekus. 



Sub-Tribe 2.— Cerucliini. 



One genus is represented in our fauna, Ceruchus, of cylindrical 

 form, with the head and mandibles of the male enlarged. There 

 are two species, G. piceus from the Atlantic, G. siriatus from 

 Oregon. 



Sub-Tribe 3.— Sinodeiidrini. 



This sub-tribe consists of but a single genus, Sinodenclron, of 

 cylindrical form ; the male has the head armed with a long horn, 

 and the anterior part of the thorax suddenly declivous ; the man- 

 dibles are short in both sexes; the eyes are not emarginate; the 

 maxillae and ligula are not concealed by the mentum. 



S. rugosum Mannh. inhabits California and Oregon. A species, 

 S. americanum, is described by Beauvois, from Atlantic America, 

 but is unknown to me. 



Tribe II.— PASSALINI. 



Ligula large, corneous, filling a quadrate emargination of the 

 mentum ; antennae straight, first joint of moderate length ; man- 

 dibles with a basal molar tooth, and an anterior movable one ; 

 maxillae with both lobes hooked ; labrum movable ; scutellum in 

 front of the base of the elytra; middle coxae nearly globular. 



This tribe contains but a single genus, of which many species 

 exist in the warmer parts of the earth ; it is represented in our 

 fauna by but one, Passalus cornutus, an elongate, somewhat flat- 

 tened, shining beetle, of large size, having the head armed with 

 a short bent hook, and the elytra deeply striate. It is epiite 

 frequently seen in old stumps of trees. 



Fam.XXZIL— SCARAB^IDAE 



Parts of the mouth variable in form. 



Antennas inserted under the sides of the front, before the 

 eyes, 7- to lL-jointed, usually 10-jointed, the external joints, 

 usually three in number (sometimes as many as seven), pro- 



