Horn.] 



128 



[Feb. 21, 



pectorcdis but less so than nebulosus. Head black, clypens black, except 

 a small space in front of the eyes. Disc of thorax clouded with fuscous- 

 Length .13 inch ; 3.3 mm. 

 This and the preceding occur in California. 



The species in which the mesosternum is cristate and the presternum 

 simple, are not so readily distinguished. 



Elytra striate, mesosternal crest spiniform bifidus. 



Elytra not striate. 



Mesosternal crest very short oehraceus. 



Mesosternal crest produced, with acute free angle. 

 Elytral margin slightly but distinctly explanate. 



Color entirely testaceous reflexipennis. 



Elytral margin not rerlexed ; color never entirely 

 testaceous. 

 Very convex species, sides of elytra almost vertical, 

 color usually very black, and shining. 

 Under edge of mesosternal crest oblique, body 



above entirely black, shining consors. 



Under edge of mesosternal crest horizontal, 



thickened, body with piceous margin ductus. 



Feebly or moderately convex species, sides of 

 elytra gradually descending, color above rarely 

 black, usually pale piceous. 

 Mesosternal plate having the anterior edge sinu- 

 ous in front, the angle very acute and not 



mucronate diffusus. 



Mucronate fuse us. 



Mesosternal plate with the anterior edge oblique 

 not sinuous, the angle very broad. 



Elongate oval perplexus. 



Broadly oval latiusculus. 



P. bifidus, Lee. Proc. Acad. 1855, p. 371. 



Elliptical, moderately convex, black, shining, thorax and elytra with 

 piceous margin. Surface moderately densely punctulate, punctures of 

 elytra coarser than those of thorax. Elytra with ten moderately deep 

 striie, the outer deeper than the inner, striae four to ten nearly entire, the 

 inner three stria? gradually shorter, sutural stria at one-fourth from apex 

 dividing into two rows of fine punctures. Body beneath black, moder- 

 ately shining. Mesosternal crest acute, spiniform. Legs piceous black, 

 tarsi paler. Second joint of maxillary palpi scarcely longer than the 

 third. Length .28 inch ; 7 mm. 



Resembles several of the species of Hydrobius but differs in the short 

 terminal joint of the palpi. The character shown by the inner stria is 

 not very evident except in immature specimens. In only one of the 

 mature specimens are there punctures, slightly coarser than those of the 



