AMERICAN COLEOPTERA. 235 



The head shows but little variation except that noted above. In 

 all the Species except optica and hituberosa the eyes form the most 

 prominent part of the sides of the head, but in these the head is 

 slightly prolonged behind the eye and a little more prominent than it. 

 In these also the muzzle is much shorter, and the antennae are in- 

 serted close to the frontal margin and more distant from the eyes than 

 in the others. 



The antennae are eleven-jointed and never elongate, the club is 

 composed of four or five joints but in some species is so gradually 

 formed as to make it difficult to determine whether it has the one or 

 other number. The terminal joint of the club is flattened, oval at tip, 

 but in opaca and hituberosa somewhat conical. 



The thorax is variable in shape but is usually transverse, rarely 

 orbicular {surinamensis), the apex emargiuate more or less distinctly 

 except in the two species above where it is truncate. 



The elytra are costate in a variable degree in all except truncafa, 

 the lateral margin reflexed, the apex is variable, squarely truncate 

 only in truncata. 



The legs present but little of note other than some sexual variation 

 which is given under the species. 



The anterior tarsi of the male and in some species the middle also 

 are dilated, while in some the dilatation is very feeble. 



After a careful study of our species I can see no valid reason for 

 adopting any of the genera into which the present has been divided. 

 To those who desire to know more of these genera the more general 

 works will give the desired information, and of these none is more 

 worthy of attention than C. G. Thomson's Skandinaviens Coleoptera, 

 a work on a small fauna, full of useful suggestions and "■ivino' evi- 

 dence of careful and patient research. 



The visibility of the prothoracic stigmata has been urged as a 

 reason for the adoption of Necrodes as a valid genus, but as Lacor- 

 daire correctly remarks S. americana has the stigmate equally visible. 

 From my observations on our species I am convinced that the visi- 

 bility of the stigmate is merely an accident depending on the size 

 and extent of the prothoracic epinieron, and the stigmate may be 

 seen in any species in which the thorax is slightly bent upward so 

 as to render the connecting membrane a little terse. I can see no 

 reason for attaching any value to this character. It must be admitted 

 that many of the characters separating the species of Silpha are such 

 as might elsewhere be deemed of generic value, but from the stand- 



