120 PROCEEDINGS OF THE NATIONAL MUSEUM vol.84 



TYNOMMA MUTANS (Chamberlin) 



Lysiopetahim mutans Chamberlin, Ann. Ent. Soc. Araer., vol. 3, p. 233, 1910. 



This species was described from female specimens collected at Stan- 

 ford, Calif., but no characters of definite generic value are given in 

 the description. The size and shape of the eye, as shown by Cham- 

 berlin's drawing, and the locality where the animals were collected 

 indicate that the species may belong to Tynomma rather than to the 

 more southern DiactLs, which has larger eyes. Wliile the female 

 organs, or ovipositors, of mutans do not closely resemble those of 

 other species of Tynomma^ they show still less similarity to those of 

 Diactis. Spirostrefhon is excluded on account of its much larger 

 size and more eastern distribution. 



COLACTIS, new genus 



Type. — Colactis saxetana^ a new species from Arizona. 



Diagnosis. — This genus, and its close relative Heptium., may be dis- 

 tinguished readily from the other American genera of this family 

 by the presence of only 10 crests on the first segment; no secondary 

 crests on segments 2, 3, and 4; abbreviated secondary crests on the 

 other segments; and 8-jointed legs on all but a few of the anterior 

 segments. In Colactis the seventh legs of the males are no smaller 

 than the other legs, but in Heptium the seventh legs of the males 

 are greatly reduced in size; and the full number of dorsal crests 

 begins on segment 18 or 19, instead of on segment 16 or 17, as in 

 Colactis. 



Description. — Body of variable size and proportions; 10 to 20 

 times as long as broad ; usually distinctly depressed, although cylin- 

 drical in one species; number of segments 49 to 89. 



Eyes triangular to quadrate, composed of 30 to 52 ocelli in 6 to 9 

 rows ; sense organ of about the size of an ocellus. 



Antennae moderately long and slender; joint 2 longest; joints 3 

 and 6 subequal and each slightly longer than joint 4; joint 6 a little 

 shorter than joint 4 and not over a third longer than the conic seventh 

 joint. 



First segment nearly semicircular; posterior portion with only 10 

 crests, in front of which are 10 setae arranged in a more or less 

 triarcuate series. 



Segments 2, 3, and 4 usually with only primary crests, but rudi- 

 ments of secondary crests occasionally may be found on segment 4. 



Transition to the full number of dorsal crests occurs on segment 

 16 or 17. 



Primary crests completely crossing the posterior subsegments, 

 somewhat thickened, the sides below the apex with one or two rows 

 of tiny circular pits. 



