228 COLEOPTERA OF NORTH AMERICA. 



Tribe II.— BOSTRICHINI. 



The insects of this ti'ibe are moderate in size, or small, of a 

 cylindrical form, with the head deflexed, prolonged behind the 

 small prominent eyes, and covered by the hood-like prolongation 

 of the prothorax; the epistoma is separated by a moderately dis- 

 tinct suture ; the anterior part of the prothorax is usually rough 

 with, tubercles, and in the genus Bostrichus is frequently pro- 

 longed, forming two short horizontal horns ; the anterior coxal 

 cavities are confluent ; the hind part of the elytra is frequently 

 obliquely declivous. The antennae have 9-11 joints in our genera, 

 and the club is 3- or 4-jointed. The external margin of the ante- 

 rior tibiffi is more or less serrate in all of our genera. 



Our genera are found in fungi, and under bark: — 



Intermediate joints of antennae shorter than the first and second. 

 Tarsi long, slender, first joint very short. 



Antennae with a three-jointed club. Sinoxylon. 



Antennae with a four-jointed club. Tetrapriocera. 



Intermediate joints of antennae longer than the first and second. 

 Tarsi as long as the tibiae, slender, second joint long. 



Front margined, at the sides at least. Bostrichus. 



Front not margined. Amphicerus. 



Tarsi short, second joint not elongated. Dinoderus. 



The type of Tetrapriocera is Bostrichus longicornia Oliv., oc- 

 curring in Florida and the West Indies. Rhizopertha has been 

 suppressed as not sufficiently distinct from Dinoderus. 



Tribe III.— PSOIIVI. 



The insects composing this tribe are of large or moderate size; 

 the thorax is oval, not margined at the sides, truncate in front, 

 not protecting the head, which is large and prominent. The club 

 of the antennae is 3-jointed. The anterior coxae are separated by 

 the prosternum. Tarsi slender, elongate, four-jointed in Psoa, 

 five-jointed in Polyeaon, the first joint being very small. 



Two genera occur in our fauna: — 



Anterior coxae separated, tibiae serrulate. Polycaon. 



Anterior coxae contiguous, tibiae slender, simple. Psoa. 



Exopioides Giirr. has been united with Polycaon, the ten-jointed 

 antennae being the differential character of the former. Acrepia 



