UNITED STATES AND MEXICAN BOUNDARY. 19 



Base of elytra truncate or sinuate Philolithus. 



bb. Mandibles and submentum contiguous Ologlyptus (Stenorides.) 



na. Anterior tibiae compressed with the apical external angle prominent. 



Posterior angles of thorax distinct. Pelecyphorus, Asida. 



Posterior angles not distinct Euschides. 



II. Antennae 10-articulate : maxillae visible in part. 



Tibiae compressed, dentate Cardigenius. 



Tibiae rounded, mutic Scotinus. 



Taking the division with 11-articulate antennae, it appears to me that a more 

 natural relation between our native genera is expressed as follows : 



A. Mentum filling the emargination of the gula. 



a. Last joint of maxillary palpi moderately dilated : mentum and mandibles approximate, leaving 



room only for the palpi. 

 Base of elytra truncate, inflexed portion broad. 



Prosternum prominent, outer apical angle of anterior tibiae prolonged Astrotus Lee. 



Prosternum not prominent, anterior tibiae truncate Pactostoma Lee. 



Base of elytra emarginate, inflexed portion narrow Microschatia Sol. 



b. Last joint of maxillary palpi very large : mentum and mandibles separated by a moderately wide 



space : inflexed portion of the elytra wide Pelecyphorus Sol. 



B. A distinct fissure between the sides of the mentum and the gula : last joint of maxillary palpi very 



large : inflexed portion of elytra wide Euschides Lee. 



The type of Astrotus is Microschatia contorta Lee. ; and of Pactostoma is Asida anasto- 

 mosis Say. 



Pelecyphorus seger , piceo-niger, subnitidus, thorace latitudine duplo breviore, antice posticeque angustato, 

 lateribus valde rotundatis depressis transversim rugosis, disco parce punctato, ad basin late emarginato, 

 angulis posticis subacutis, elytris ovatis convexis postice valde declivibus, sutura, costis dorsalibus 

 duabus ante apicem confluentibus margineque elevatis obtusis interstitiis insequalibus haud punctatis : 

 subtus parce punctatus, epipleuris inaequalibusimpunctatis. Long. -75. 



Llano Estacado, Capt. Pope. Closely related to P. sordidus Lee, but differs 

 by the disc of the thorax being only distantly punctured, while in that species the 

 punctures are large, close and confluent. The under surface is likewise less densely 

 punctured, and the epipleurse are almost entirely free from punctures. The costae 

 of the elytra are broader and obtuse. 



Pelecyphorus ir regularis, piceo niger nitidus, thorace latitudine plus duplo breviore, antice angustato, 

 lateribus rotundatis depressis transversim rugosis, disco sat dense punctato, ad basin late vix emarginato, 

 angulis posticis subacutis, elytris ovatis convexis postice valde declivibus, sutura costis duabus ante 

 apicem confluentibus margineque elevatis, interstitiis valde insequalibus, impunctatis; subtus punctatus, 

 epipleuris punctis paucis notatis. Long. -81. 



Llano Estacado, Capt. Pope. Also related to P. sordidus, but the sides of the 

 thorax are less rounded, the base is hardly narrowed, and the disc is less densely, 

 less coarsely and not confidently punctured. 



