included in the genus Tropisternus. 115 



coxa becomes gradually narrower, but is not so abruptly 

 turned in, till just before the extremity, where it is folded 

 in and applied to the inner face, as in Tropisternus. 



The two species are peculiar by their rather broad 

 form, much attenuate behind ; they are very distinct 

 from one another, Tropisternus obscurus having the 

 swimming-legs rather stout and their tibiae ciliate, whereas 

 in Pleurhomus sahlbergi the swimming-legs are slender 

 and their tibiae entirely destitute of cilise ; thus the two 

 species form two sections similar to what obtains in 

 Tropisternus. In both species the pubescent area at the 

 base of the hind femur is quite small. 



1. Pleurhomus sahlbergi, n. s. 



Ovalis, convexus, posterius attenuatus, pernitidus, 

 supra fusco-seneus, antennis, palpis pedibusque anteri- 

 oribus testaceis, pedibus posterioribus piceis ; elytris 

 sparsim punctatis. Long. 6£ mm., lat. 3g- mm. 



Brazil. 



The punctuation of the upper surface in this species 

 is quite distinct, but is rather more sparing than usual, 

 especially on the wing-cases, where, too, the punctures 

 are not all of one size, there being distinctly larger 

 punctures scattered amongst the finer ones. The syste- 

 matic punctures on the side of the thorax form a short 

 line, and the epipleural margin is without the least trace 

 of sculpture or spines. The sternal spine is short, flat, 

 and punctate, and there is not the least trace of any 

 carina on the last ventral segment. The hind legs are 

 very slender, the upper-inner face of their tibiae is 

 extremely polished and without any trace of ciliation. 



I have a single individual of this remarkable little 

 species sent to me by Prof. Sahlberg, of Helsingfors, as 

 No. 2881 ; it was discovered by his father at Santa Eita, 

 in Brazil, in September, 1850. 



2. Tropisternus obscurus, Sharp. 



Sharp, Biol. Cent. Am., i., pt. 2, p. 60, pi. ii., f. 7. 



Guatemala. 



In this species the punctuation of the upper surface 

 is very fine, and is evenly distributed, except that it is 

 denser on the head and thorax than it is on the wing- 

 cases ; the systematic punctures on the side of the 



