110 PROCEEDINGS OF THE NATIONAL MUSEUM vol.84 



Type.— Mule, U.S.N.M. no. 1237. 



Reinarks. — The type locality is Pierce, Wliarton County, Tex., 

 where a single male was collected in December 1905 by Dr. O. F. 

 Cook. Many other specimens were collected the same year at Whar- 

 ton, Tex., on the bank of the Colorado River. In 1927 additional 

 specimens were collected by Dr. Cook in Smith, Dallas, and Tarrant 

 Counties, Tex. 



DIACTIS, new genus 



Type. — Diactis soleata^ a new species from southern California. 



Diagnosis. — From Tynomina this genus is distinguished by the 

 extremely divergent inner primary crests of segments 2, 3, and 4; 

 the more numerous ocelli; and, in the males, by the lobed coxae of 

 the seventh legs and of the anterior legs on the segments near the 

 middle of the body. 



Description. — Body moderately slender, 12 to 15 times as long as 

 broad, slightly flattened, composed of 48 to 54 segments. 



Eyes triangular, composed of 35 to 48 ocelli in 6 to 9 rows; sense 

 organ distinctly larger than an ocellus, its diameter nearly equal to 

 the distance between the eye and the base of the antenna. 



Antennae subclavate; joint 2 longest; joints 3 and 5 subequal, 

 longer than joint 4, which is longer than joint 6; joint 7 more than 

 half as long as joint 6. « 



First segment with 18 low longitudinal crests posteriorly, the me- 

 dian crests not extending forward beyond the basal fourth of the 

 segment; lateral crests but slightly longer; in front of the crests 10 

 setae are arranged in a transverse triarcuate series extending for- 

 ward and inward from near the hind angle on each side; counting 

 from the angle the fourth seta on each side is set far behind the 

 third seta but not quite so far behind the fifth seta, which is very 

 close to the middle of the segment. 



Segments 2, 3, and 4 with the inner pair of primary crests four to 

 eight times as widely separated behind as in front ; the two secondary 

 crests between them small and parallel, but the other secondary 

 crests are larger and oblique, as are the primary crests; behind 

 segment 4 the inner primary crests are nearly parallel. 



Transition to the full number of dorsal crests occurs on segment 

 8 or 9. 



Primary crests thin and of uniform height at the apex, which is 

 smooth; crests usually more strongly developed on the caudal seg- 

 ments. Secondary crests usually reaching the posterior margin of 

 the segments, diminishing in size and becoming inconspicuous on the 

 last segments. Sides of both primary and secondary crests and the 

 intervals between them definitely and uniformly netted. The setae 



