18 GEO. H. HORN, M. D. 



the deeper the siiuiation the wider the border, so that in those species 

 with the feeble sinuation the border is very narrow. The apical edge 

 has nearly always a pellucid border. 



The sculpture of the disc of the thorax is important in the sepa- 

 tion of the species, and consists of impressed lines or fovese, which 

 are apparently merely a modification of the simpler forms observed 

 in Helophorus. There is, in the first place, the median impressed 

 line, which may be quite a deep channel or a feeble line. In sculptus 

 this line is practically obliterated, while in Hobnbergi it is very short. 

 Secondly, on each side of the median line are the discal fovese, Avhich 

 are more or less deep, and vary in form and size. These have a 

 tendency to revert to the simple lineate type of Helophorus, as may 

 be traced through paneticollis to sculptus and lineatus. Rarely these 

 discal fovese are entirely wanting, as in cribricoUis. External to the 

 discal are the lateral impressions, which are more or less oblique in 

 position and variable in dei)th, and in Icempennis existing as a mere 

 trace. 



The elytral sculpture exhibits the usual variation of the striato- 

 punctate type, the stride varying in depth and the punctures in size, 

 depth and approximation. 



The lateral margin of the elytra is slightly explanate, usually 

 from the humeri to the middle, or slightly beyond, but in benefossu-s 

 extending to the apex. 



The species of Ochthebius at present known to me may be recog- 

 nized by the following table : 



Lateral margin of elytra explanate from the humerus to apex. 



( Cyrtochthebius ) 

 Thorax deeply sinuate at posterior half, the transparent border very narrow; 



all the donsal foveffi deep benerossiiiii. 



Lateral margin explanate from humerus to middle or beyond, but never to apex. .2. 



2. — Thorax abruptly siuuately narrowing from one-third or less posterior to the 



apical angle, and with a pronounced angulation at middle of sinuation ; 



transparent border broad (Odontochthebiusj 3. 



Thorax abruptly sinuate from the middle, or deeply notched near the hind 

 angles; transparent border broad. 



Thorax with well marked discal foveas (Trymochthebius) 4. 



Thorax without discal fovese (Homalochthebius) 5. 



Thorax gradually sinuately narrowed from apex to base; transparent border 



narrow (Ochthebius) 6. 



3.— Thorax with all the discal depressions well marked; elytra with stria" of 

 closely placed punctures; margin of pellucid border continuous. 



foveicollis. 



Thorax with very feeble discal impressions, the surface polished ; elytra 



almost absolutely smooth ; pellucid margin sinuous. ..Itevipeiinis. 



