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Physical descriptionThis extensive genus is almost peculiar to our region, as in addition to those here enumerated, two species of it from the United States of North America are all that are known. It is, however, extremely close to the Palæarctic genus Barynotus—so much so indeed, that I do not myself see any satisfactory way of distinguishing the two.
The genus is a peculiarly difficult one to deal with, the sexes of some species differing greatly in size and form. But these sexual distinctions seem to be by no means constant, while in allied species they are yet of a slightly different nature; thus it is extremely difficult to decide, from the inspection of a few specimens, where the specific limits should be drawn.
I divide the genus, in the hope of facilitating the determination of the species, into three groups, one of which is natural and easily recognized; on the other hand, the distinction between the second and third groups is a very vague and variable one.