WICKHAM: NEW MIOCENE COLEOPTERA FROM FLORISSANT. 427 



The beetle is surely a small dytiscid and since it bears so close a 

 resemblance to recent species of Bidessus it seems well to refer it here. 

 Considering the small size, it is fairly well preserved. It is one of the 

 smallest insects known from the Florissant shales. 



COELAMBUS MIOCENUS Wickham. 



One specimen, No. 2,432 M. C. Z. (No. 5,869 S. H. Scudder Coll.) 

 in poorer preservation than the type. 



HYDROPORUS SEDIMENTORUM, sp. nov. 

 Plate 1, fig. 2. 



Form short and stout, something like that of the recent H. rivalis 

 and allied species. Head large. Prothorax distorted, but evidently 

 nearly three times as broad as long. Coxal plates strongly and 

 coarsely punctured, the punctures more or less confluent. Sternum 

 between the plates similarly but hardly as strongly or thickly punctate, 

 abdominal sculpture much finer. Hind leg stout. Length, as pre- 

 served, 3.25 mm. 



Described from one specimen. 



Type. No. 2,433 M. C. Z. Florissant, Col. (No. 2,905 S. H. Scud- 

 der Coll.). 



Distinguishable at first sight from Coelambus miocenus by the dif- 

 ferent form of the coxal plates as well as by that of the body. The 

 state of preservation is not very satisfactory but I think that the 

 outlines of the structures of the underside are properly delineated. 

 None of the characters of the upper surface can be made out. I 

 use the term Hydroporus in a broad sense, not being able to determine 

 which of the genera of Hydroporini this insect should enter. 



HYDROPHILIDAE. 



TROPISTERNUS LIMITATUS Scudder. 

 One specimen, No. 2,434 (No. 3,807 S. H. Scudder Coll.). 



TROPISTERNUS VANUS Scudder. 



The only specimen No. 2,435 M. C. Z. is without original number 

 and is evidently the counterpart of the one figured by Scudder. 



