AMERICAN COLEOPTERA. 6 



entirely obliterated {gemma). The upper side has, in a general way 

 a similarity of sculpture. There is a broad triangular impression at 

 middle and an oblique impression on each side terminating in a fovea 

 at base, in all tbose species with u depressed thorax. In the convex 

 species these impressions are reduced so that there are merely three 

 basal foveae. In width there is also considerable diversity, a moderate 

 number have the tborax wider than the elytra, in others the sides are 

 regularly and gradually arcuate from tip to base. 



The prosternum exhibits remarkable differences. The simplest form 

 is that in which the apex of thorax is almost squarely truncate so that 

 the margin above and beneath is continuous, the angles of the pro- 

 sternum being prolonged so as to touch the angles of the thorax. 

 The next form is that in which the angles of the thorax are produced 

 partly concealing the eyes, the thorax above emarginate and the alae 

 or angles of prosternum not attaiiiing the angles. The form naturally 

 following this has a similar form but the edge of the prosternum is 

 trisinuate, the middle portion, immediately behind the head broadly 

 emarginate and limited on each side by a tooth of variable promi- 

 nence. Another modification results from the presence of a lobe at 

 the middle of the prosternum of moderate extent, emarginate and 

 angulate, external to which the prosternum is slightly notched the alae 

 however attaining the angles of the thorax. 



The elytra are variable in form to a moderate degree and may be 

 depressed or not, the surface is marked with striae of punctures also 

 variable, the intervals in several species subcostiform. The base is 

 truncate, except in (jibhida in which the middle is slightly arcuate 

 forward and the humeral angles prolonged, slightly clasping the base 

 of the thorax. 



The abdomen varies in punctuation, usually the punctures are 

 sparsely placed, equally over the entire surface. In pubiventris and 

 comata however the sides are more densely punctured and the pubes- 

 cence also denser and longer. In <juttif< ra the last three segments are 

 very densely and finely punctured and in vrrsuta the last two but not 

 as densely or finely as (juttlfera. 



The last ventral segment has, in many species, close to the apical 

 margin and parallel with it an elevated plate of varying extent, some- 

 times reduced to a mere subapical ridge. In a number of species 

 however it is entirely absent. When fully developed this plate causes 

 the apical margin to appear double and the term is so used in the 

 following pages. 



