376 CASEY 



last antennal joint are very pronounced. Abnorme, castaneum 

 and bi'cvifenne are probably represented at present by unique 

 females, and the inference is that in the ahnorme group of the 

 above table, the last antennal joint is very abnormally developed 

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

 dti7n 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 Prometopion 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 Tri- 

 entoma were described b}' 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 fitting into the 

 reentrant sinus at the base of the epistoma and each with a very 

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

 and both fitting closely to the epistomal apex when closed, the 

 mandibular apices rapidly though slightly deflexed and feebly 

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

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

 outer three joints slightly wider, the eleventh short and obtuse ; 

 eyes moderately developed, coarsely faceted, rather prominent and 

 but feebly emarginate anteriorly ; prothorax closely fitted to the 

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

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

 tibicE short, broadenino^ 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 ; metasternum slightly shorter than 

 the first ventral segment Trientoma 



