108 NEOTROPICAL PSELAPHIDAE 



four-segmented, with the distal segment elongate-oval, rather thick and acum- 

 inate. Ventral surface of the head with capitulate setae (a melbaform trend). 

 Pronotum with the disc simple, not foveate or sulcate ; the base with a trans- 

 verse sulcus, usually arcuate or biarcuate, posteriorly angulated at middle, ex- 

 tending to a lateral fovea each side ; these lateral foveae are usually pubescent. 

 Prosternum not medianly longitudinally carinate. Elytra with two to three 

 basal foveae on each elytron, plus a subhumeral fovea and a longitudinal sub- 

 epipleural carina and sulcus. Abdomen with six sternites in the female, and 

 seven sternites in the male; male seventh sternite in the form of the simple, 

 asymmetrically articulated, one-plate pygidium found in Melba. First tergite 

 usually provided with a pair of short, basal, discal carinae. 



Rafifray (1904) divided the then known species of this genus into four 

 groups, and since a neotropical species is known from each of the first three 

 only, this group key will serve to isolate the neotropical forms known at this 

 time: 



First tergite with a pair of basal discal carinae, second tergite with 



no basal discal carinae 2 



First and second tergites each with a pair of basal discal carinae ; each 



elytron with three basal foveae trimiiforme (Reitter) Group I 



(Valdivia, Chile) 



2. Each elytron with three basal foveae gracili Raffray, Group II 



(Chile) 



Each elytron with two basal foveae caviceps Raffray, Group III 



(Mexico) 



The three species of the region under examination may be listed as follows: 



caviceps Raffray. 1898. Mexico. 



gracili Raffray. 1898. Chile. 



trimiiforme (Reitter). 1885. Chile. (Pseudoplectus) 



ACTINOMA (Raffray, 1898) 

 obesum Raffray. 1898. Mexico. Genotype. 



PSEUDOTRIMIUM (Raffray, 1898) 

 microcephalum Raffray. 1898. Probably Mexico. Genotype. 



TRIMIODINA (Raffray, 1898) 

 concolor (Sharp). 1887. Guatemala. [Trimium). Genotype. 



TRIMIOPSIS (Reitter, 1882) 



This wholly neotropical genus has been strictly limited by Raffray (1908), 

 and now includes two species from Guatemala so inadequately described that 



