HYDROPHILID.E. 39 



TROPISTERNUS Solier. 



This is an American genus, of which nearly half the species (about a 

 dozen) occur in the United States. Four fossil species are known from the 

 early Tertiaries of Wyoming and Colorado. 



Tropisternus sculptilis. 



Tropisternm saidptilis ^cu.M., Bull. U. S. Geol. Geogr. Surv. Terr., IV, 760 (1878); 

 Tert. Ins. N..A., 514-516, pi. 7, fig. 33(1890). 



Grreen River, Wyoming. 



Tropisternus saxialis. 



Tropisternus saxialis'iicnM. , Bull. U. S. Geol. Geogr. Surv. Terr., IV, 759-760 (1878); 

 Tert. Ins. N. A., 515, pi. 8, fig. 2 (1890). 



Green River, Wyoming. 



Tropisternus vanus sp. nov. 



Pi. V, fig. 1. 



The specimen referred here apparently belongs to this genus, although 

 the scutellum is of a somewhat smaller size than is characteristic of this 

 genus and the sculpturing of the elytra is unusual. The length of the 

 abdomen is doubtless due to accident, the character of the elytral tips 

 indicating that they embraced its extremity. The form of the body and, 

 with the above accidental exception, its several regions correspond closely 

 to Tropisternus, though by the flattening of the head, which brings the 

 labrum (not separately indicated in the figure) upon the same plane, the 

 head is made to have an abnormal length. The eyes are large but scarcely 

 protrude beyond the general curve of the side of the head. The prothorax 

 shows a delicate margination laterally and exceedingly delicate wavy striate 

 markings, as if longitudinally combed, hardly observable under an ordinary 

 lens, instead of the minute punctuation usually found in Tropisternus. 

 There is also observable along the middle line on the posterior half of the 

 pronotum and the anterior part of the abdomen a slight carination, which is 

 probably the impression of the sternal carina characteristic of this group of 

 Hydrophilidfp. The elytra are rather short, their outer edge very delicately 



