50 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



mucro to the apex of the second tooth; the outer lamella, from the 

 base to the lateral tooth. Rami of tenaculum quadridentate; corpus 

 with one curving ventral seta. Clothing (pi. 18, fig. 189) of dense, 

 short, cur\ang, simple setae; sensory setae outstanding, relatively 

 short, curving or straight, simple. Integument of the adult smooth 

 but reticulate. Length, 1.4 mm. 



Remarks. — At the base of the furcula is the sam.e accessory sclerite 

 that occurs in Guthriella (pi. 9, fig. 89). 



The cotypes came from Prof. E. G. Titus, for whom the species is 

 named. 



From Prof. E. O. Essig I received a large number of specimens of 

 tliis species, all of which were, however, young individuals, ranging 

 up to 0.6 mm in length. These specimens, in alcohol, were purple- 

 lake in color, Mdth the terga bordered narrowly with darker purple; 

 antennae purple, legs pale purple, furcula white. Ungues relatively 

 stouter than in the adults, with the inner tooth often obscure or un- 

 developed. Dentes dorsally with about ten evident semicircular 

 transverse intermediate folds, running into larger irregular folds proxi- 

 mally and distally. 



Cotypes— U.S. ISIM. no. 42987. 



Distribution. — Recorded as follows: 



Utah: Petersboro, October 24, E. G. Titus. 



California: San Luis Obispo County, February 20, on surface of water, E. O. 

 Essig. 



PROISOTOMA (PROISOTOMA) LONGISPINA (MacGUlivray) 



Plate 18, Figures 190, 191; Plate 19, Figures 192-197 



Achorutes longispinus MacGillivray, 1893, p. 315. 



Description. — General color blackish purple; alcoholic specimens 

 show a violaceous tinge; legs and furcula pale. Head and second to 

 seventh segments, inclusive, each bordered posteriorly with a blacldsh 

 band. Head relatively large, one-tliird as long as body, with a sub- 

 triangular frontal projection, laterally pigmented, between the an- 

 tennae (pi. 18, fig. 190). Eyes (pi. 18, fig. 191) eight on each side, 

 equal, on black patches near the antennae. Postantennal organ (pi. 

 18, fig. 191) narrowly subelhptical or subreniform, three to four times 

 as long as the diameter of an eye. Antennae inserted in excavations 

 on each side of the frontal projection, shghtly longer than the head, 

 with all the segments telescopic, and in relative lengths about as 

 2:4:3:5; second and third segments dilated distally; fourth subclavate, 

 rounded apically; first three segments ringed with black apically; 

 fourth black apically. Sense organ of third antennal segment v/itli 

 a pair of linear curving sense rods subtended by a chitinous ridge. 

 Fourth antennal segment with olfactory setae. Body subcylindrical; 

 prothorax concealed from above. Fourth abdominal segment longer 

 than the third (as 7:4). Genital and anal segments ankylosed dor- 



