2 BULLETIN 138, UNITED STATES NATIONAL MUSEUM 



Therefore it is not surprising that the accumulated material 

 jdelded 91 species, of which 54 are described as new. In order to 

 make this report complete for the region involved, those species de- 

 scribed by Woodward, Whiteaves, and Gabb have been included in 

 the list. This brings the total number of known species for the West 

 Coast up to 105. The area covered extends from the oil fields of 

 Alaska (Controller Bay region) to the northern part of Lower 

 California, and embraces the Cretaceous. Tertiar3\ and Pleistocene. 



Fossil remains of Crustacea are rare. Their shells are so fragile 

 that they are easily destroyed. Only the hardest parts, such as the 

 chelae, the terminal articles of the walking legs, and less often the 

 sternum are ordinarily preserved. Entire specimens of the body 

 with attached appendages are seldom found except singly in the in- 

 terior of concretions. 



To such concretions is due the preservation of more than 200 

 specimens of Zanthopsis vulgaris. This appears to have been the 

 common crab of the Oligocene in British Columbia, Washington, 

 and Oregon, and has no counterpart at the present day. The aver- 

 age size varies from about fi/^ to 2 inches across the back and in one 

 case reaches 3 inches. The largest nodule measures 19 centimeters in 

 its greatest diameter and weighs Wy-2 pounds. The species forms a 

 third of the bulk of Pacific material examined. 



The next most abundant species represented is a fresh-water 

 crayfish from eastern Oregon and southwestern Idaho, Astacus 

 chenoder-ma. A mass of material from the Yale Museum demon- 

 strates the identity of this species with ^1. Ijremforceps Cope, which 

 was founded on the smaller of a pair of asymmetrical chelae. 



Worthy of note is the prevalence of members of the family 

 Raninidae beginning with the Eocene. The family is not now living 

 on the west coast of America north of Mexico. 



Two species of Stomatopoda are here described, the first to be 

 found fossil in America. 



In the several lists which follow are given not only the new dis- 

 coveries and the extent of the relationships of the various species but 

 also a summary of their geologic occurrence. The manuscript was 

 submitted to Prof. Bruce L. Clark and Miss Nellie M. Tegland, 

 research assistant in paleontology at the University of California, 

 who have corrected the horizons according to the latest researches. 

 In sj)ite of the number of species it is to be regretted that the 

 paucity of material makes it impossible to draw any broad general 

 conclusions. 



In order to render this paper of the greatest possible use to in- 

 terested workers, brief characterizations of the major groups have 

 been introduced. 



For full data regarding the various specimens, see under list of 

 localities, pages 11 to 22. 



