THE CANADIAN ENTOMOLOGIST. 153 



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1882. Sharp, David. On Aquatic Carnivorous Coleoptera or Dytis- 

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1883. Horn, G. H. Miscellaneous Notes and Short Studies of North 

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ON TWO NEW SPECIES OF PL.\TYCERUS. 



BY THOS. L. CASEY, U. S. A., NORFOLK, VA. 



I am scarcely warranted in attempting a detailed table of this genus, 

 because a number of species are known to me only by a single sex ; but 

 in looking over the material, it can be readily perceived that there are two 

 sections, the first represented by quercus, oregonensis and depressus, being 

 characterized by great sexual differences in the mandibles, and the 

 second, represented by all the other species, having the mandibles 

 unmodified in the male. The second section may be divided into three 

 groups : the first, represented by Agassii, pacificus a.nd pat-vicollis, which, 

 judging by analogy, have the hind tarsi long and slender in both sexes ; 

 the second, composed of californicus and thoracicus, having the hind 

 tarsi short, at least in the female ; and the third, with stout and triangular 

 tibiae, at present represented by Keeni alone. 



The name of this genus is changed in the recent Catalogue of 

 European Coleoptera, to Systenocenis, Weise, but while admitting the 

 validity of the change, I do not think that Platycerus should include the 

 species called Lucanus, by Scopoli and others, because it is probable that 

 Geoffroy did not describe any species under the name Platycerus, and the 

 genus Platycerus, Geoff., should therefore be regarded as not published. 

 I have not been able to consult the original work of Geoffroy, however, and 

 am not certain that my premises are correct. 



P. Keenly n. sp. — Body very stout, convex, polished, blackish- 

 castaneous in colour. Head small, coarsely and confluently punctate, 

 two oblique subelevated areas of the occiput subimpunctate ; mandibles 

 very small, the internal tooth at the middle small and broadly triangular ; 

 antennae short, rufo-testaceous, the scape slightly longer than the funicle, 

 the latter compact, the three outer joints increasing gradually in width 

 but not prolonged ; club short, abrupt, compact, not so long as the funicle, 

 three-jointed, the first abruptly, more than twice as wide as the last joint 



