126 PROCEEDINGS OF THE NATIONAL MUSEUM vol.84 



posterior half of the bodj^, the rim around the impression very 

 strongly swollen and witli niimerons scattered j)its. The two pri- 

 mary crests below the lateral carinae distinctly more conspicuous 

 than those on the dorsum and with the apex slightly more irregular 

 in outline, faintly subdentate. 



Anterior subsegments with tlie posterior channels subquadrate, 

 very slightly longer than broad, and separated by distinct beaded 

 lines; bottom of the channels appreciably more finely reticulated 

 than the surface of the segment in front of them. 



Last segment rather broadly rounded behind, subtruncate, with 12 

 dorsal setae in addition to the two apical papillate hairs. 



Anal valves with the margins thinly raised, the disk of each valve 

 strongl}'^ convex. 



Gonopods somewhat resembling those of profenta but the ex- 

 panded apical portion of each erect piece is more oblique and is 

 broadly rounded distally ; the outer arm on each erect piece is shorter 

 and more slender, and the apposed prongs at the end are smaller 

 (% 16, i). 



Males and females with a comb of hairs beneath the outer joint 

 of the anterior legs, as in the other species, but the males have the 

 velutinous pads on 6 to 20 pairs of legs behind the genitalia, in addi- 

 tion to the four pairs immediately in front of them. 



ry;>e.— Male, U.S.N.M. no. 1245. 



Remarks. — Numerous specimens collected in the Estrella Moun- 

 tains, Maricopa County, the type locality, and in the Table Top 

 Mountains, Pinal County, Ariz., February 13, 1929, by R. H. Peebles 

 and H. F. Loomis. Many specimens also were collected in the Kofa 

 Mountains, Ymna County, Ariz., March 31, 1930, by R. H. Peebles 

 and H. F. Loomis, extending the range for this species over a greater 

 area than that of any other member of the family in the Southwest. 



COLACTIS PROTENTA, new species 



FiGtTEE 16, g-4; Plate 3, Figuke 3 



Diagnosis. — Not only is this the largest species of Colactis^ but it 

 is also the largest member of the family in North America, some 

 specimens exceeding by 10 mm the largest Spirostrephon. Specific 

 characters not shown by other members of the genus are the bowed 

 imier pair of crests of the first segment, the rounded lateral carinae, 

 and the transition to the full number of dorsal crests on segment 17, 

 instead of on segment 16. 



Description. — Body moderately slender, 40 to 50 mm long and 2 

 to 2.5 mm broad; strongly depressed, especially the females, which 

 are not so conspicuously constricted behind the first segment as the 

 males; segments 70 to 89 (pi. 3, fig. 3). 



