164 MEMOIRS ON THE COLEOPTERA 



that of any Atlantic coast form of Discoderus known to me, and 

 the sinus of the elytra could hardly be described even as slight; it 

 is the merest vestige, which would be unobservable unless looked 

 for very sharply. 



In Bull. Mosc. 1859, p. 137, Motschulsky describes a Pangus 

 americanus, which is evidently a Discoderus and it is correctly 

 assigned to that genus in the Munich catalogue. The type was 

 given to the describer by Dupont, as coming from California, but, 

 as the genus Discoderus does not seem to occur in California, the 

 Dupont specimen was in all probability incorrectly labeled and 

 might have been from almost any other locality in North America. 

 As Motschulsky 's description fits parallelus very well, I think there 

 can be no lack of propriety in assigning it as a synonym of that 

 species as proposed above. 



Horn describes the prothorax of robustus (Bull. Bk. Ent. Soc., 

 VI, p. 52) as being "distinctly narrower at base than at apex," 

 which could only be the result of an optical illusion; the prothorax 

 is, if anything, a little wider at base than at apex, though the two 

 are very nearly equal, as stated in the table. Pinguis Csy., which 

 was united with robustus by Dr. Horn, is a very different species, 

 having the prothorax notably narrowed at apex and with the forma- 

 tion of the basal margin and the extent of its medial sinuation 

 altogether at variance with the corresponding characters in robustus. 

 Piceus, of the table, is held to have a value at least subspecific, 

 because of the differences stated, which are quite apparent in series; 

 robustus seems to be much more constantly deep black above and 

 piceous-black beneath. The presence of fine suffused setigerous 

 punctuation at the sides and apex of the elytra in most of the 

 species of this genus does not seem to have been noted heretofore; 

 this feature is similar to that observed in the genus Selenophorus, 

 indicating another bond of affinity. It will also be observed that 

 the head is distinctly larger in the female than in the male in many 

 species, as in Stenomorphus. The descriptions of crassicollis and 

 tenebrosus are taken from the originals, as I do not have these 

 species at hand. 



The genus Trichopselaphus Chd., has some peculiar male sexual 

 characters, the arcuation of the hind tibiae in that sex being analo- 

 gous to the similar arcuation of the intermediate tibiae in Discoderus, 



