CETONIIN^E 347 



well as its very different habitat, is probably abundantly distinct 

 from planata, whether depressa is really identical with the latter 

 or not; no accurate description of the remarkable anterior tarsus 

 is given by either author. 



Cremastocheilus Knoch. 



This is the typical genus and probably also the largest of the 

 tribe; it is wholly confined to subarctic North America. Among 

 the African genera Scaptobius Schaum, resembles it most closely, 

 but even here it is merely a question of outline and subsimilarity of 

 the hind thoracic angles, as the sculpture is of an entirely different 

 order. The head in Cremastocheilus differs very much from that 

 in any of the preceding genera, the vertex and front being uniformly 

 convex, not at all carinate along the sides and sloping more or less 

 abruptly anteriorly to the reflexed clypeus. The tarsi are varied in 

 form, sometimes very short and compact as in schaumi, thence 

 becoming longer, though still compact, as in westwoodi, to a rather 

 long and slender form as in canaliculatus, or what is termed "ambu- 

 latorial" by Horn, though just why the short tarsi of schaumi will 

 not admit of ambulatorial progress just as well, is not exactly clear. 

 The anterior tibiae are bi- or tridentate, the latter condition very 

 rare but distinctly developed in tridens. 



The mentum is deeply concave as a rule, but may be flat, with 

 reflexed posterior edges, this being probably often influenced by 

 sex, since both forms occur occasionally in the same species, as for 

 example in schaumi. In certain species, principally eastern, the 

 mentum has a large deep posterior sinus; in others, such as squamu- 

 losus, this sinus becomes very small though still deep; in others, as 

 variolosus, still smaller and at the same time shallower; again, as in 

 schaumi, the sinus wholly disappears, leaving a rounded posterior 

 edge and finally, in still other species, such as knochi, almost wholly 

 western in habitat, the posterior edge becomes prominently angu- 

 late at the middle. It is because of this inconstancy that I am 

 unable to admit the validity, even subgenerically, of the name 

 MyrmecoconuS' subsequently altered by pen in distributed separata 

 to Myrmeceicon recently proposed by Mr. W. M. Mann (Psyche, 

 XXI, p. 179), to include those species having the mental plate 

 entire and angulate behind. The author definitely stated the type 

 of his new subdivision of the genus, leaving thus no doubt of his 



