430 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 57. 



belonging to Xylonomus in its strictest sense. " From this is to be 

 seen that the long recognized name Xylonomus will have to be 

 placed as a synonym of Xorides and the group which Gravenhorst 

 considered as Xorides will have to be known as Deuteroxorides 

 Viereck. 



Cresson^ was the first American author to recognize this gi-oup as 

 occm-ring in the Western Hemisphere. Later ^ he listed and tabulated 

 the American species. Since then the group has been recognized 

 correctly by all American writers under the name Xylonomus and 

 the species were again tabulated by Harrington ^ when he described 

 canadensis. Later Davis described two species (catomus and maudae) 

 and in 1913* Rohwer described seven species and endeavored to use 

 as subgenera certain of the genera erected by Foerster. 



The shape, length and carination of the first tergite of the female 

 offers very valuable specific characters yet there is such a gradation 

 from a short medianly constricted and dorsally carinate to a long 

 gradually widening noncarinate segment that no tangible group- 

 ing can be made on this character alone. Again there is such antig- 

 eny in the length and sculpture of the tergites that this character 

 cannot be used in grouping the species. Foerster would restrict 

 Xylonomus to those forms in which the first tergite is constricted 

 medianly, but this restriction can not be used with any reliance 

 without first removing difficult species. Rohwer^ proposed to sep- 

 arate Moerophora from Xylonomus s. s. by the relative length of 

 the second tergite as compared with its apical width — a character 

 used by Foerster to separate Sichelia from Rhadina — but this 

 character, although useful, can not be strictly applied and is 

 available only in the female. The secondary sexual character used 

 by Foerster to separate Sterotriclius can not be considered of generic 

 value; nor is the position of the nervulus, as compared with the basal, 

 as employed by Foerster to separate off Gonophonus, a sufficiently 

 stable character to be used generically. If this last-mentioned 

 character were used it would be necessary to erect new ''genera" and 

 it would widely separate species which are otherwise rather closely 

 allied. Or, to express it briefly, the writer does not believe that any 

 of Foerster's segregates of Xylonomus when defined only on the char- 

 acters he uses can be considered as natm-al groups sufficiently dis- 

 tinct to be treated as genera. They seem to be a hasty expression 

 of characters which may distinguish the various species groups found 

 in Europe. Our American species fall into a number of natural groups, 

 some of which are probably the same as the Em'opean groups, while 

 others are different from the European groups and if we were to name 

 all of them we would need a number of new names. The genotypes 



> Proc. Ent. Soc. Phila., vol. 4, 1865, p. 288. * Proc. U. S. Nat. Mus., vol. 45, pp. 353-358. 



s Trans. Amer. Ent. Soc, 1870, p. 167 and p. 172. 'Idem, vol. 45, 1913, p. 353. 



8 l ** Ent., vol. 23, 1891, p. 134. 



