424 Materials for a Monograph 



Bacteria femordla, Ilaldenian in Icon. Eiicyc. (1857.) 



Bacmiculus femoratus, Uhler in Harris, Inj. Ins., 3d ed. ; 



146. (1861.) 



Mass., (H. Coll., Sanborn, S. H. S.) N. II., (H. Coll.) 

 Illinois, (Uhler.) Red River Settlements, British America, 

 (S. H. S.) Nebraska, (Mus. Comp. Zoul.) 



GRYLLIDES, Latreille. 

 TRIDACTYLUS, OLIVIER. 



The fact that this name is inapplicable in its significa- 

 tion to some of the species contained in it, is no valid rea- 

 son for its disuse ; and even should it be so considered, the 

 name Heteropus proposed as early as 1805 by Palisot de 

 Beauvais, must supersede that of Xya, so commonly in 

 use, which was not proposed till four years later. If, 

 however, the species having but two of the slender appen- 

 dages at the termination of the posterior tibiae should be 

 found to differ generically from those having three, Tri- 

 dactylus would have to be retained for the latter, with 

 Heteropus as a synonym ; and Xya should be applied to 

 the former. That this may yet be found to be the truth, 

 is indicated still further by the fact that the three-fingered 

 species found in this country have a peculiar conformation 

 of the anterior tibiae, which, however, is a feature of the 

 structure of the male alone, — a fact for which I am in- 

 debted to the scrutiny and kind communication of Mr. 

 Uhler ; this peculiarity is a lateral projection of an ad- 

 uncate appendage inwards at the base, to the extremity of 

 which, beside the hook, the tarsi are attached. As a fig- 

 ure will explain much better than any description I can 

 give the form of these parts, I have drawn the anterior 

 tibiae and tarsi of T. apicalis, Say ^. In the two 

 species ( T. apicalis, Say, and T. terminalis, Uhl.) 

 which show this character, a further difference is to 

 be seen between the males and females, in the more 

 I'ig- 1- swollen prothorax of the former. 



