STATE GEOLOGIST. 233 



above by a spined plate of the last thoracic segment; length about iVo 

 cm. excluding setge. 



This species appears not to be very abundant, or at least from its 

 small size it is not often encountered. A few particulars distinguish 

 these western forms from the description given by Brady, among them 

 being the spinous armature of the stjdets, the bristles on the penulti- 

 nate segment of the abdomen, pectinate bristles of the fifth feet, and 

 the greater length of the abdomen, yet I see no reason for separating 

 them. I have not seen the male and can not be sure that there is no 

 further development, but the fact that the feet in this form are three" 

 jointed, and its peculiar characters, clearly distinguish the species 

 from any other known to me. 



