166 Journal New York Entomological Society. ^^°^- xxvi. 



narrow, bifid at apex, and projecting obliquely backwards, the elytra 



margined with yellow. Length 4.5 mm. (Tex.) S. fossiger Lee. 



The anterior process projecting well backwards and overlapping the pos- 

 terior, the posterior a broad plate that ends outwardly in a blunt 

 tooth and a sharp spine, elytra unicolorous. Length 3.75 mm. (Hot 

 Springs, Ariz.) S. tricornis n, sp. 



23 — Prothorax entirely orange, apical margin of same reflexed and extended 

 laterally, so as to form well defined lobes, the posterior process broader 

 than the anterior (of armature), the pronotal disc with shallow lunar 



fossa 24 



Prothorax an orange-red margined with black, apical prothoracic margins 

 less reflexed and not expanded laterally into lobes, the posterior 

 process much narrower than anterior, the pronotal disc with shallow 

 circular fossa 25 



24 — Posterior process but little wider than the anterior, the posterior angles 

 some distance from process, black with dull yellow prothorax. Length 



3.5 mm. (Eastern States.) S. bidentata Say. 



Posterior process more than twice the width of anterior, the posterior 

 angles overlapping base of posterior process, black with reddish yellow 

 prothorax. Length 4.5-5.5 mm. (Ind., Kan., Mo.).. .S. latiloba Blatch. 



25. — (Middle and Southern Cal.) S. obtusa Lee. 



Silis spinigera Lee. 



Silts spinigera Lee, Trans. Amer. Ent. Soc, Vol. V (1S74), p. 61; 



Trans. Amer. Ent. Soc., Vol. IX (1881), p. 56. 

 Silis munita Lee, Trans. Amer. Ent. Soc., Vol. IX (18S1), p. 56. 



These two, as surmised by LeConte, are merely color phases of 

 one species. It is truly dichromatic in most parts of its range. It is 

 also our largest species and the only one in which the prothorax of 

 the male is always distinctly narrower than the base of the elytra. 

 The eyes are prominent, together as broad as the interocular area; 

 the antennae fully three fourths the length of the body; the prothorax 

 one fourth broader than long, with the sides slightly rounded in front 

 and shallowly excavated at the posterior angles, the anterior bound- 

 ary of the incisure rounded and the process a broad plate bifurcating 

 externally into an anterior sharp horizontal spine and a posterior 

 prong, the hind angles small and blunt, almost concealed by the prong 

 of the process, the base broadly rounded, the disc feebly convex with 

 the longitudinal impression defined posteriorly and a deep fovea just 

 within the incisure as well as an acute tubercle just anterior; the 

 elytra at base one fourth wider than prothorax and seven times as 

 long and slightly scabrous. (Plate IX, fig. i.) 



