No. 453.] DISTRIBUTION OF CICINDELA. 



specimens this knob is largely developed though not hooklike, in 

 others it disappears entirely, so that the descending ]xirt of the 

 band is of nearly uniform size to the tip. None of the .speci- 

 mens in my series show a strong tendency towards the willisto)ii 

 type of marking, the lead to that form going through C. echo. 

 But some of the pscudoseiiilis approximate the Saltair C. echo so 

 closely that if they were mixed they could scarcely be separated 

 again. The shores of Owens Lake, in southeastern California, 

 are the only definitely known haunts of the true C. psciidosenilis, 

 though Dr. Howard writes me that in the National Museum is 

 a single specimen said to have been taken by Mr. Coquillet in 

 Los Angeles County — not very far distant. None of the other 

 Californian collectors have found it in this latter lo'cality, how- 

 ever. I found it in great abundance about the overflow of a 

 spring on the upper beaches of Owens Lake, but none occurred 

 in the immediate vicinity of the bitter waters of the lake itself. 



Now that the variations of the insects have been described, 

 we must turn again to the geological records and see what can 

 be said of the early conditions of the country they inhabit. 

 The geology of the Great Basin has been worked out by Dr. G. 

 K. Gilbert.i and Dr. Israel C. Russell,^ the results of their 

 labors appearing in two fine volumes from which the main geo- 

 logical items used in this discussion are compiled. We find 

 that in the early Pleistocene the basin held two great fresh- 

 water lakes: Bonneville, covering the greater part of western 

 Utah and a small portion of eastern Nevada and southern Idaho, 

 and Lahontan, occupying an extensi\ e area m western Xex ada 

 and eastern California. Between them lava bioad plateau or 

 divide, forming a watershed, the hydrographic basin-, ot the hikes 

 being contiguous. Both of these lakes were of irregular sliai)e, 

 Lahontan being especially so, with numerous arms and bays 

 extending up narrow, flooded valleys. Each lake had two great 

 periods of high water, which had been preceded b\- times of 

 drought and desiccation, the second stage of Hood being higher 

 than the first. These times of plenty correspond to the two 



