338 On Aquatic Carnivorous Coleoptera or Dytiscide. 
qd Pp U] 
I. 20.—Genus PACH YDRUS. 
Labrum concealed, only its front margin and fringes being visible; middle coxe 
rather widely separated; prosternal process broader than long, its obtuse hind 
margin reaching the metasternum ; hind tibiz 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 Dytiscidee, 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 
subineequali, fortiter irregulariter punctato ; elytris crebre, grosse punctatis, punctis 
elongatis. Long. 4, lat. 23 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 coxz are somewhat coarsely punctured: 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 Rita, 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 
subineequali, crebre irregulariter punctato; elytris dense, fortiter profandeque 
punctatis. Long. 33, lat. 22 m.m. 
This species is a good deal shorter than P. punctatus, to which it 1s 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, (?U. 8., 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 Aubé, (No. 1463) ; Antilles. 
