538 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.52. 



I have five males and one female of this species from the lower end 

 of Truckee River where it flows through the desert just before enter- 

 ing Pyramid Lake. One male and three females were taken on the 

 Humboldt River at Carlin, Nevada. All the specimens were taken 

 on gravel bars near rapids. The habits were similar to those of hison 

 and severus. These desert specimens agree in their large size and 

 ashy coloration, but structurally no character seems to separate them 

 from morrisoni. The usual types of appendages fomid in morrisoni 

 are shown in figures 172-173, but an occasional morrisoni regular in 

 color and size has appendages as shown in figure 177, where the 

 superiors are more pointed and the inferior is shorter than the supe- 

 riors. The usual forms of appendages of nevadensis are shown in 

 figures 180-181, but one nevadensis male, regular in size and colora- 

 tion, has appendages as in figure 185, v^dth the inferiors distinctly 

 longer than the superiors. Neither are the forms of hamules and 

 seminal vesicle constant. This variety then differs from morrisoni in 

 the larger size and paler coloration, and from severus in having 

 pointed posterior hamules.^ (Fig. 182, vulva; 183, female occiput.) 



OPHIOGOMPHUS ARIZONICUS, new species. 



Type. — Cat. No. 21142, U.S.N.M. A male, Huachuca Mountains, 

 Arizona, F. H. Snow. 



Allotype. — Cat. No. 21142, U.S.N.M. A female, Huachuca Moun- 

 tains, Arizona, F. H. Snow. 



Color in dried specimens, i/<7?g. ^Thorax and abdominal segments 1 

 and 2 olive, abdomen yellow, marldngs black. (See fig. 198.) 



Face greenish yellow; eyes brown (probably gray in life); a 

 black line, interrupted medially, on the posterior edge of the hori- 

 zontal surface of the frons; vertex black, inclosing an oval pale area 

 posterior to the ocelli; occiput pale; rear of head yellow, with a 

 large T-shaped black marking. Prothorax largely black. Meso- 

 thorax and metathorax olive green (probably bright green m young 

 live specimens), with dark brown marldngs as follows: A spot on 

 upper end of middorsal keel, antealer ridges and upper third of hum- 

 eral suture narrowly brown (in one male entire humeral suture brown). 

 A small oval spot, or in one male a comma-shaped spot, on the upper 

 end of the mesepisternum. Lower edge of mesepimeron black, 

 pruinose. A small fleck anterior and one posterior to the lateral 

 spiracle. Legs creamy; distal fourth of femur black, which extends 

 mesad along the dorsal surface of the femur to the trochanter, this 

 stripe broadest on the fore legs; tibiae black with an external pale 

 stripe; tarsi black. 



1 1 thought at first that this was a distinct species, as I found a single exuvia on the Truckee River 

 undoubtedly ol this species and differing markedly from those of morrisoni. However, I found nevadensis 

 common on Owens River in eastern California during August, 1915, and seined up several nymphs which 

 are almost identical with those of morrisoni. See p. 6i9, footnote. 



