A revision of the spider genera Drassodes and Tivodrassus (Araneae, Gnaphosidae) in North AmericaBy Norman Platnick & Mohammad Shadab
American Museum Novitates No. 2593
Includes species descriptions with genitalic diagrams and range maps for the seven described species of North American Drassodes
. The genus Tivodrassus
does not occur within Bug Guide's range, but this paper also includes the descriptions and diagrams for the four known species.
This paper is available online thru the AMNH Research Library: http://digitallibrary.amnh.org/dspace/bitstream/2246/2976/1/N2593.pdf