308 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



the male, interrupted on all segments. Length, $. 8.5-9 mm ; $ 8.5-10 mm . 

 Two males and eight females. 



16. Cyrtopogon rattus n. sp., & 9. — Altogether covered with yel- 

 lowish-gray pollen ; thorax with a geminate black line in the middle ; 

 abdominal segments on each side anteriorly with a shining black spot. 

 Length 9-10 mm . 



Face and front grayish-pollinose, the former with a white inystax ; the 

 bristles above the mouth are black ; ocellar tubercle and occiput beset 

 with whitish hairs ; a small tuft of black hairs on each side of the vertex 

 near the upper corner of the eye. Thorax gray, with a black double 

 line in the middle, abbreviated before reaching the scutelluin ; the lat- 

 eral stripes are paler brown, ill-defined, and crossed transversely by the 

 grayish-pollinose thoracic suture. The pile on the thorax is whitish an- 

 teriorly, black posteriorly ; bristles black. Scutellum gray, clothed with 

 long, soft, whitish pile. The fan-like fringe of hairs in front of the hal- 

 teresis white. Abdomen gray, clothed with soft, whitish pile ; segments 

 2-6 on each side at the base with a large shining black spot, diminish- 

 ing in size on each subsequent segment. In the female, these spots are 

 much smaller. The seventh segment, in the female, is black, shining ; 

 the hypopygium of the male is also free of pollen, but beset with yel- 

 lowish-white pile. Legs black, beset with long, white pile; bristles on the 

 tibiae also white, except the terminal ones and those on the front side 

 of the front pair. Halteres with a lemon-yellow knob. Wings hyaline ; 

 veins black, normal. 



Sab. — Webber Lake, Sierra County, California, July 22. Five males 

 and one female. The autennal style is comparatively shorter here than 

 in all the preceding species, somewhat coalesceut with the third joint; 

 the bristle at its tip is very distinct. 



17. Cyrtopogon cerussatus n. sp., $ 9 . — Black; thorax whitish-pol- 

 linose ; abdomen with white cross-bands on the anterior margin of seg- 

 ments 2-6 ; the sides of the same segments posteriorly each with a large 

 white spot ; wings hyaline ; legs black, with white hairs. Length 6.5-8 mm . 



Face covered with a white, hoary pollen ; mystax black, more dense 

 immediately above the mouth than higher up ; facial gibbosity rather 

 fiat, little prominent; antennae black, third joint three times the length 

 of the two first taken together, narrow, almost linear ; the style is very 

 short, perhaps one-tenth of the length of the joint, cylindrical, with a 

 minute bristle; ocellar tubercle rather large and broad, with deep 

 grooves on each side between it and the orbit of the eye ; both the 

 tubercle and the opposite side of the groove are beset with black pile, 

 which, commingling, form a distinct tuft on the top of the head; on 

 each side of this tuft, along the orbit of the eye, there is a narrow mar- 

 gin of minute microscopic yellowish-white hairs ; lower down, on the 

 orbit, on a level with the antennae, there is, on each side, a small tuber- 

 cle, the upper and outer side of which is clothed with the same micro- 

 scopic yellowish-white pile ; the occiput is beset with white hairs, except 



