AMERICAN OOLEOPTERA. 251 



The genera of this tribe may bo divided io groups in the following 

 manner : 



Abdomen with six segments. 



Posterior coxffl distinctly separated but in a variable degree; elytra usually 

 without sutural stria; antennae slender and long. 



Head oval, without eyes Bathvsci.e. 



Head broad, narrowed to a neck behind and with eyes Platycoolei. 



Posterior coxse contiguous; elytra with sutural stria usually deeply impressed ; 

 antennse more or less elavate; head suddenly narrowed behind the eyes 



forming a neck, the occiput elevated in a ridge Cholev.b. 



Abdomen with five segments (often four in 5 )• 

 Posterior coxse contiguous; elytra with sutural stria well marked; head oval 

 not narrowed behind, eyes round and moderately prominent, occiput not 

 elevated Colones. 



The above division in groups seems absolutely necessary, not only 

 for greater convenience of study but also from the fact that the genera 

 included in each represent quite distinct types. 



The groups are also very naturally interlinked, the second possess- 

 ing many important characters of the first and third, while the fourth 

 seems to be related to the third through Camv-us* Sharp. 



The first group contains all the eyeless genera, (Adelops having 

 eyes), the species living for the most part in caves. As yet our 

 country possesses no members of it. 



The genera of the group Bathysci^ are all European and it might 

 seem out of place to discuss them here, but the study of them has 

 proven so interesting that I have thought it profitable to review them, 

 as their occurrence in some of our caves is possible. 



Before proceeding with the discussion it is important to note that 

 Adelops does not belong to the group. This genus was founded on a 

 species (hirtus), from the Mammoth Cave of Kentucky, which must 

 under all circumstances bear the generic name. The European species 

 included in Adelops are members of another and probably of two 

 genera, as will be seen further on. Leptodirus and Bathyscia were 

 the only genera known at the time of the publication of Lacordaire's 

 genera, the second having been improperly suppressed into Adelops^ 

 Pholeiion Hampe, Oryotus and Drimeotus Miller, were subsequently 

 described without any reference to their relationship to Leptodirus. 



To Mr. Schaufuss (Stettin Zeitschr. 1861, p. 424, et. seq.), is due 

 the credit of associating them in a group, to which he adds two new 

 genera through a misconception of the characters of Adelops and 

 Bathyscia. 



* Ent. Mo. Mag. June, 1876, p. 23. 



