338 Oil Aquatic Carnivorous Coleoptcra or Dytiscidw. 



I. 20.— Genus PACHYDRUS. 



Labrum concealed, only its front margin and fringes being visible ; middle coxae 

 rather widely separated; prosternal process broader than long, its obtuse hind 

 margin reaching the metasternum ; hind tibia3 straight, their basal portion not 

 conspicuously narrower than the apical one. 



Five species from tropical America and the Antilles are included in this genus ;'"' 

 they are very similar to one another in most respects ; the punctuation of their 

 wingcases is much coarser than is usual in the Dytiscidse, and the species are best 

 distinguished from one another by a reference to this character. 



224. Pachydrus punctatus, n. sp. — Ovalis, nitidus, convexus, latus, piceus, capite 

 thoraceque dilutioribus, antennis pedibusque rufo-testaceis ; prothorace superficie 

 subintequali, fortiter irregulariter punctato ; elytris crebre, grosse punctatis, ]")unctis 

 elongatis. Long. 4, lat. 2| m.m. 



Head somewhat finely, but quite distinctly and moderately closely punctured. 

 Thorax with the surface obscurely wrinkled, and distinctly and rather coarsely 

 punctured, the punctures being irregularly distributed, so as to leave small, smooth 

 spaces. Elytra very coarsely punctured, the punctures being elongate in the 

 longitudinal direction, this is most strikingly seen on their basal half, the punctua- 

 tion at the sides is finer and dense, the humeral portions are paler than the rest. 

 The outer portions of the hind coxse are somewhat coarsely j^unctured : the 

 metasternum is only very obsoletely punctured. 



In this species and its allies I have not detected any external marks to distinguish 

 the sexes. 



Brazil. (Santa Eita, September, 1850, Sahlberg; Rio de Janeiro). 48. 



225. Pachydrus cribratus, n. sp. — Ovalis, subopacus, latus, brevis, piceus, capite 

 thoraceque dilutioribus, antennis pedibusque rufo-testaceis ; prothorace superficie 

 subinjEquali, crebre irregulariter punctato ; elytris dense, fortiter profandeque 

 punctatis. Long. 3|, lat. 2^ m.m. 



This species is a good deal shorter than P. punctatus, to which it is very closely 

 allied, but is very readily distinguished by the sculpture of the upper surface, 

 which is closer, the punctures on the elytra show no elongation. 



Mexico ; Castleton, Q. U. S., N. America) ; Guadeloupe. 49. 



• The following two species' descriptions probably refer to insects of this genus ; Hyphydrus cayennensis 

 Cast., (No. 1461 huj. op.) ; South America. — Hyphydrus globosus Aube, (No. 1403); Antilles. 



