160 H. C. FALL. 



The relation of cinereum to its congeners is, however, still proble- 

 matical. If the specimen be really a male as supposed by Horn, and 

 the pectinate antennae would seem to indicate this, then it is perhaps 

 identical with desertum, all known examples of which are appar- 

 ently females. All these latter are, however, considerably smaller 

 than the Texas male, and are known from the California desert.?. 

 They show scarcely a trace of the evident though vague elytral 

 costae of cinereum. If, on the other hand, the type of cinereum be 

 a female it must be that of laticeps — if of any here made known, the 

 pectination of the antennae of the latter being much longer. The 

 emarginate last ventral of cinereum is of doubtful signification. 

 Usually this is a male character, but in laticeps, which is unques- 

 tionably a male, this segment is evenly rounded behind, and more- 

 over the last ventral of cinereum is fringed internally with capitate 

 hairs, very similar in structure to those which I have previously 

 referred to * in the females of Chalcolepidius, Tragidion, etc. A 

 character of this sort would be expected to prevail throughout a 

 genus, but there is no trace of such hairs in other females of Xera- 

 nobium. In view of these uncertainties I have thought best that 

 each of these forms should stand with a name of its own, until fresh 

 material of both sexes shall enable us to solve the puzzle. 



4. X. desertum n. sp. — Similar in color and vestiture to laticeps and mac- 

 rum, but evidently more robust than either. The antennae (fig. 22) are rather 

 shorter than in macrum, being scarcely more than one-third as long as the body, 

 but are similar in structure. The head is distinctly narrower than the protho- 

 rax, the front twice as wide as the longest diameter of the eye. The prothorax 

 is relatively wider than in the two preceding species, being approximately two- 

 thirds as long as wide, with the sides moderately rounded, the base and apex 

 subequal in width. Elytra slightly more than three times as long as wide, the 

 sutural margins divaricate from apical fourth or fifth ; surface throughout appar- 

 ently finely scabrous and dull, the head with minute scattered polished granules. 

 The presternum is not so long before the coxee as in the two preceding species, 

 the length being scarcely greater than the thickness of the coxa. Last ventral 

 segment very broadly but evenly rounded at tip. Length 7-7.5 mm. 



California, Salton, two females (Hubbard); Mojave, one female; 

 Needles, one female (Wickham). 



The Salton specimens, which are to be regarded as types, were 

 bred from stems of Allenrolfea occidentalis sent to Washington by 

 Mr. Hubbard. Mr. Schwarz refers them f to Ctenobium cinereum 



* Ent. News, IX, p. 239, Dec. 1898. 

 t Proc. Wash. Ent. Soc, IV, p. 377. 



