Sept.-Dec, I9i8.] VaN DyKE : REVIEW OF GeNUS SiLIS. 163 



species and is in fact the most conspicuous differential character, so 

 the details of its structure are particularly dwelt upon in the defini- 

 tion of the species. 



In this paper, complete descriptions of only the new species will 

 be given. The others will, however, be discussed in some detail 

 which, with the synoptic table and outline drawings of the male pro- 

 thorax, will. I think, make their identification possible. A large 

 number of specimens has been at my disposal and served as the basis 

 for this paper. Besides my own large series, chiefly from the Pacific 

 Coast, I have examined the specimens in the collections of Dr. F. E. 

 Blaisdell, Mr. H. C. Fall, Mr. Ralph Hopping, Cornell University, 

 and the bulk of those in the United States National Museum, the last 

 received through the courtesy of Dr. E. A. Schwarz and Mr. H. S. 

 Barber. The LeConte types in the Museum of Comparative Zoology 

 at Harvard University, I have also been enabled to study through 

 the kindness of Mr. Samuel Henshaw and Mr. Nathan Banks, and 

 have likewise seen accurately determined specimens of Mr. Charles 

 Schaeffer's species received through the generosity of the describer 

 himself. To the above-mentioned institutions and friends, as well as 

 others who have helped me in my work, I therefore now wish to 

 express my thanks. 



Table for the Determination of the Species of Silis Latr. 

 Based Mainly upon Male Characters. 



Lateral prothoracic armature situated at or close to the hind angles i 



Lateral prothoracic armature situated distinctly in front of the hind 



angles (Ditemnns Lee.) i8 



I — The posterior appendage of the armature slightly ante-basal and con- 

 spicuously spinose 2 



The posterior appendage of the armature either basal or slightly ante-basal 



but not sharply spinose 5 



2 — Prothorax narrower than base of elytra and with the process in the form 

 of a broad plate derived from the side of the prothorax and to a great 

 extent filling the incisure, its outer face prolonged into a superior 

 horizontal spine and an inferior prong, the latter close to the hind angle 

 of the prothorax. Length 8 mm 3 



Prothorax fully as wide at base as base of elytra and with a distinct 

 ante-basal process that is spiniform and that arises close to but below 



the posterior angles. Length 6-7 mm 4 



3 — Yellow testaceous, head, antennae, and legs more or less duslcy, prothorax 

 orange yellow. Length 8 mm. (Or., high Sierras of Cal., and 

 Utah) S. spinigera Lee. 



