152 THE CANADIAN ENTOMOLOGIST. 



Darker, slightly larger, more densely punctured ; the mark on the 



vertex is not defined, the thoracic lines are broader and the femora nearly 



black. The sulci of the $ elytra are more abbreviated at base, while in 



the (^ the tufts of hair on the inner edge of the three basal joints of the 



intermediate tarsi are much less developed than in semisulcatus. Fraternus^ 



Harr. 



Thermonectes, Esch. 



Only one Canadian form, T. basilar is, Harr., a somewhat convex 

 beetle, blackish above ; head with the front and a transverse line on the 

 vertex fulvous, thorax with sides and a median transverse line of the same 

 colour. Elytra with the external margin, a sub-basal fascia and some 

 vague irrorations yellowish. .36-40 in. 



Graphoderes, Esch. 



Thorax fulvous, black on anterior and posterior margins ; head yellowish, 

 the occiput and an M-like mark black. .50 in cinereus, Linn. 



Smaller, testaceous, beneath rufous ; head in front, sides of thorax and of 



elytra yellowish. .46 in liberus. Say. 



According to late authorities, the Y\dAVitfasciatocoUis should give way 



to cifiereus, and I have accordingly used the latter. 



Cybister, Curt. 

 One very large insect, C. fimbriolatics, Say, represents the genus 

 with us. It is of ovate form, nearly black, but with a greenish cast, the 

 sides of the thorax and elytra with a broad yellow margin. In the 9 the 

 wing covers and thorax are finely strigose with short lines, the sutural 

 region smoother. Length, about 1.20 in. 



The following are the titles of the more important works treating of 

 the American forms of the Dytiscidse and Haliplidie. All have been freely 

 used in the preparation of the foregoing pages : — 



1838. Aube., Ch. Species general des Hydrocanthares et Gyriniens. 

 Paris. 



1855. Leconte, J. L. Analytical table of the species of Hydroporus 

 found in the United States, with descriptions of new species. Proc. Acad. 

 Nat. Sci., Phila., VIL, pp. 290-299, 



1862. Leconte, J. L, Synopsis of the species of Colymbetes inhabit- 

 ing America north of Mexico. Proc. Acad. Nat. Sci., Phila., pp. 



521-523- 



