20 GEO. H. HORN, M. D. 



Group F. 



Scutellum small. Head convex, without trace of frontal tubercles, 

 the clypeus feebly emarginate. Anterior tibia? tridentate and crenate 

 externally, the first tarsal joint shorter than the second. Posterior 

 tibite fimbriate at apex with short equal spinules, the first tarsal joint 

 but little longer than the next two. Mesosternum not carinate. 



This group was originally suggested by Dr. LeConte for obtusus 

 (Hayden's Surv. 1878, Bull, iv, 2, p. 454), to which I find it neces- 

 sary to add three others. Two of these are species formerly placed 

 by me in the series with unequal spinules, partly on account of the 

 poor material then in hand and partly by the judgment of Dr. Le- 

 Conte, who indicated that position for sulxjeneiis (Pacif R. R. Rep. 

 47 paral. Insects, p. 42). There can be no doubt, however, that the 

 spinules are short, closely placed and as nearly equal among them- 

 selves as possible. 



The following table will enable the species to be recognized : 



Thorax with marginal line at base. 



Marginal line very fine, but entire; general color brownish, elytra dull yellow; 



thorax sparsely punctate obtusus. 



Marginal line deep and well marked ; head and thorax black, the latter mod- 

 erately closely and rather coarsely punctate coiisociatus. 



Thorax with marginal basal line visible at sides only. 



Intervals of elytra sparsely moderately punctate, the second and fourth in- 

 tervals rugulose and opaque subseneus. 



Intervals of elytra irregularly biseriately punctate, the punctures nearly as 



coarse as those of the stripe, intervals not rugulose alternatus. 



These species are all from the region west of the Mississippi, ex- 

 tending from the Rocky Mountains to the Pacific coast. 



A. obtusus Lee— Moderately elongate and convex, brownish, moderately 

 shining, elytra dull yellow or luteous. sides of thorax always paler, femora dull 

 yellow, tibige darker. Antenute entirely pale. Head dark brown, almost piceous 

 the entire margin paler, front not tuberculate, almost smooth at middle closely 

 punctate at sides and in front; clypeus very feebly emarginate, angles obtuse, 

 sides slightly arcuate, gense moderately prominent, obtuse. Thorax slightly 

 narrowed in front, sides feebly arcuate in front, straight posteriorly,'hind angles 

 obtusely rounded, base arcuate with fine distinct marginal line, disc moderately 

 convex, sparsely punctate, a little more closely at the sides, with extremely fine 

 punctures intermixed. Elytra a little wider at base than the thorax, humeri 

 very obtuse, disc feebly striate, stria^ closely finely punctate, intervals slightly 

 convex, sparsely punctulate. Body beneath sparsely indistinctly punctate. 

 Mesosternum coarsely punctate, a median oval opaque space divided by a fine 

 groove. Anterior tibife smooth in front, tridentate externally and crenulate 

 above, the first tarsal joint shorter than the second. Posterior femora very 

 sparsely punctate, the first tarsal joint shorter than the next three. Length 

 .24-26 inch; .6-6.5 mm. 



