376 CASEY 



last antennal joint are very pronounced. Ahnorme^ castaneum 

 and brcvifcnne are probably represented at present by unique 

 females, and the inference is that in the abnoi'me group of the 

 above table, the last antennal joint is very abnormally developed 

 in both sexes, though especially in the male, while in the /«///*- 

 dum group, these departures from the normal are not so pro- 

 nounced, or, in other words, it is presumable that the last an- 

 tennal joint of the female in the first group is about as elongated 

 as in the male of the second. In the genus Pronietopion this 

 abnormality in the terminal joint does not exist at all, as far as 



we know. 



Tribe Trientomini. 



A single genus, containing a moderate number of species, 

 confined to the fauna of the Caribbean regions, alone constitutes 

 this tribe so far as now known. Two Mexican species of Tj'i- 

 entoma were described by Mr. Champion in the " Biologia," 

 but in the appendix of the volume, were considered by that 

 author to have been wrongly labeled and in reality collected in 

 San Domingo. The tribe is a very satisfactory link between the 

 previous tribal groups and the Gnathosiini, and is the only one 

 of the subfamily, except the Epitragini and several with small 

 mentum, occurring in the Caribbean fauna. The genus may 

 be described as follows : — 



Body oval, compact, glabrous, wingless, the epistoma strongly pro- 

 duced, narrowed toward base, abruptly and transversely truncate, 

 the mandibles very thick, with a basal swelling fittinj>^ into the 

 reentrant sinus at the base of the epistoma and each with a ver}' 

 thick, strong, obtuse tooth, that of the right slightly the larger 

 and both fitting closelv to the epistonial apex when closed, the 

 mandibular apices rapidly though slightly deflexed and feebly 

 bifid at tip ; mentum transverse, hexagonal, with the apox feebly 

 sinuate ; antenna; rather thick but cylindric, subglabrous, with the 

 oviter three joints slightlv wider, the eleventh short and obtuse; 

 eyes moderatelv developed, coarsely faceted, rather prominent and 

 but feeblv eniarp^inate anteriorlv ; prothorax closelv fitted to the 

 elytra and as wide at base as the base of the latter ; scutelluni very 

 minute; elytra finely margined at base, with serial punctures; 

 tibiae short, broadening; from base to apex, the external angle of the 

 anterior not prolonged; tarsi short, thick, the basal joint of the 

 posterior almost as long as the entire remainder; intercoxal pro- 

 cess of the abdomen obtuse; mctasternum slightlv shorter than 

 the first ventral sesfment Trientoma 



