DYSTTSCnXE HYDROPHILID^E. 37 



AGABUS Leach. 



A richly endowed cosmopolitan genus, of which nearly fifty species are 

 found in North America. In the older Tertiaries a single species has been 

 found at Rott and another at Florissant, while it is reported from amber. 

 Two existing- species have been credited to the Pleistocene of England and 

 five described from that of Galiria. 



AGABUS RATHBUNI sp. nov. 

 I'l. IV. tur. 4. 



The structure of the under surface of this beetle, as shown in the 

 figure, leaves no doubt of its belonging to the dytiscid tribe Colymbetini, 

 and the form of the lateral wing of the metasternum with the carinate pro- 

 notum refers it to Agabus. Naturally there is little on the under surface to 

 distinguish species in a group so abundant in forms as Agabus, but it may 

 be said that it has a broadly ovate form, approaching the shape of the 

 GyrinicUe in its posterior breadth and narrowing anterior portions; the 

 hind legs are rather stout, though not large, and the hind coxae and anterior 

 half (at least) of the abdomen are very distantly, arcuately, and exceed- 

 ing!}" finely striate. 



Length, 7.5 mm.; breadth, 4.5 mm. 



Florissant, Colorado: one specimen, No. 1906. 



Named for my zoological friend, Richard Rathbun, of Washington. 



DYTISCID^E sp. 

 PI. IV, figs. 3. 5. 



The figures represent the metasternum of a species of this family, per- 

 haps a Matus, which is described in a section on the Pleistocene beetles of 

 Fort River in Monograph XXIX of the United States Geological Survey, 

 by Prof. B. K. Emerson (pp. 740-746). 



Hadley, Massachusetts. 



As nearly all Tertiary insects are found in fresh-water deposits, one 

 would naturally look for members of this group therein and would expect 

 their absence from amber. This expectation is realized. Seventy-four 



