30 



HYDROPHILID^. 



b. Intermediate furrows on the thorax 

 nearly as straight as the dorsal one . 

 2. Alternate interstices of elytra not cari- 

 niform and setose. 



A. Last joint of maxillary palpi sym- 

 metrically fusiform. Eleventh elytral 

 interstice not cariniform 



B. Last joint of maxillary palpi more 

 convex on the outer than on the inner 

 side, the latter neai-ly straight. Eleventh 

 elytral interstice cariniform. 



a. Joints 2-4 of the hind tai'si succes- 

 sively deci'easing in length, the second 

 hardly IJ times as long as the third. 

 Hind margin of the last ventral seg- 

 ment evidently denticulate . 



b. Second joint of the hind tarsi more 

 than 1^ times as long as the third, the 

 latter a little longer than the foui'th. 

 Hind margin of the last ventral segment 

 nearly entire ..... 



IT. Elytra without a scutellary stria, 

 i. Last joint of maxillary palpi symmetric- 

 ally fusiform. 



1. Thorax coarsely granulate throughout, 

 its sides strongly rounded before the 

 middle, the subsequent narrowing ex- 

 cavate ....... 



2. Thorax coarsely granulate at the sides 

 only, which are moderately rounded 

 before the middle with the subsequent 

 narrowing straight .... 



ii. Last joint of the maxillary palpi more 

 convex on the outer than the inner side, 

 the latter nearly straight. 

 1. Thorax widest before the middle. 

 A. The longitudinal furrow on the head 

 widened in front, 

 a. Elytra dark brown with an oblique 

 suffused patch on the basal third, 

 another near the middle of the outer 

 margin, and a sharply-defined roundish 

 spot near the apical fifth next the 

 suture, on each, yellow 



H. NUBILUS, Fah. 



H. INTERMEDIUS, Muls. 



(alternans, Gene.) 



H. AQUATICUS, L. 



H. AQUATICUS, VAR. 



.EQUALis, Thorns. 



H. ARVERNICUS, Muls. 



H, BREviPALPis, Bedel, 



H.QUADRISIGNATUS, Bach, 



{dorsalis, Brit. Cat.) 



