HYDROPHILIDjE. 4 7 



Antennae with first joint very long. Cyllidium. 

 Antennae with first joint moderate ; 



Maxillary palpi with last three joints equal. Spkkchopsis. 



Maxillary palpi with last joint longest. Philhydeus. 



Maxillary palpi with the 3d joint longer than the 4th. Hydrobius. 



The type of Sperchopsis is $perc7iews tesselatus Ziegler, a very- 

 rare insect of the Atlantic district. 



In Hydrobius subcupreus the third and fourth joints of the 

 antennae are closely united, so that I formerly described them as 

 8-jointed. Cyllidium contains small hemispherical species, re- 

 markable for having the first and second ventral segments covered 

 by large plates, ciliate with hairs proceeding from the base of the 

 abdomen, which thus appears to have but four ventral segments ; 

 the hind tarsi are short, by which they are distinguished at first 

 sight from Laccobius. 



Tribe IV.— sni.r.RBDIIM. 



Small terrestrial species, of an oval, convex, or hemispherical 

 form, living in the excrements of herbivorous mammals ; the color 

 is usually black, with the elytra frequently spotted or margined 

 with yellow ; the elytra have ten rows of punctures or striae, but 

 in Cyclonotum arc entirely without striae. Our species of Cercyon 

 are not yet properly investigated ; several of them have been 

 imported from Europe. 



Maxillae with lobes coriaceous, or submembranous ; antennae 

 9-jointed in our genera ; second joint of maxillary palpi thick- 

 ened ; legs not natatorial ; first joint of middle and posterior tarsi 

 elongated. 



Except Sphaeridium,* all the known genera of this tribe have 

 been found in the United States. They are distinguished as 

 follows : — 



Mesosternum narrow ; 



Mesosternuni produced in front. Cyclonotum. 



Mesosternum not produced ; presternum carinate. Cercyon. 

 Mesosternum very wide ; 



Prothorax margined. Megasternum. 



Prothorax not margined. Cryptopleprum. 



* I have a specimen of the European Sphceridium scarahaoidcs, found in 

 Canada. The species is undoubtedly introduced, and accidental in occur- 

 rence. It is described by Beauvois under the name S. crenatum. The 

 genus differs from Cercyon by the antennae having only eight joints. 



