NORTH AMERICAX COLEOPTEUA. 93 



althoui^h several have distinct ol)li(iiie ridges. The tarsi of the pos- 

 terior legs are short, the joints flattened, the first elongate triangular, 

 the last very short and small, the claws minute, often entirely lost, 

 apparently by use. 



As all the species have the margin of the thorax find)riate with 

 slender hairs no mention of this is made in the specific descriptions. 



The species seem to indicate the affinities of the genus in three 

 directions: — bldens, with the cylindrical forms of Aegialia and more 

 remotely with Atsenius — cegialioides, quinqueplicatus and especially 

 interruptus with Rhyssemus, while ccelatus and hydropicu.<i resemble 

 the robust Aegialiix;. 



The maxillary structure is the only decisive character for separa- 

 ting the genus, but in our fiiuna the short compressed hind tai'si with 

 triangular joints will readily distinguish it from either Rhyssemus or 

 Pleui'ophorus. 



Authors do not seem to be in accord as to the limits of the genus. 

 Harold, in the Catalogus and later, includes Pleurophorus, but the 

 characters of this seem to be as well defined as several other univer- 

 sally recognized genera and will be retained in the present essay as 

 distinct. 



The species known at this time, although few in number, are about 

 as numerous as those found in Europe ; they may be separated in the 

 following manner : 



Form oblong 2. 



Form short, elytra inflated 4. 



2.— Clypeus with a small reflexed tooth each side of the broad emarjrination : 



disc of thorax comparatively smooth bideiis. 



Clypeus obtusely atigulate each side ; disc of thorax roughly sculptured 3. 



3.— Disc of thorax with transverse grooves more or less distinct. 



Occiput with deep oblique grooves arranged in chevron; thoracic ridges 



sharply defined SPgialioides. 



Occiput without oblique grooves. 



Elytral intervals convex with few or no simi)le punctures; color ferru- 

 ginous moderately shining quinqueplicatus. 



Elytral intervals with a series of indistinct tlattcncd tubercles; color 



brownish, with a pale elytra, subopaque interruptus. 



Disc of thorax very coarsely, irregularly and sparsely jtunctate ; species very 



small nanus. 



4.— Thorax with two deep transverse grooves at sides, the one post-apical, the 

 other slightly in front of middle; posterior tibise with olilique ridges. 



oielatus. 

 Thorax without transverse grooves; posterior tiliiie without oblique ridges. 



hydropic US. 



