Art. XVII.— On a Crayfish from the liOirer Tertiary 

 heds of Western Wyoinin§^. 



By A. S. Packard, Jr. 



The discovery of two well preserved specimens of crayfish from the 

 Lower Tertiary beds of the western border of Wyoming Territory is 

 notable from the fact that while fossil crayfishes of the Cretaceous and 

 of probable Pliocene age were known, hitherto none have been found in 

 the Lower Tertiary deposits. The locality from which the specimens 

 were brought is the fish beds of the Bear Eiver Valley, situated from 

 75 to 100 miles a little west of north of Evanston, Wyo., and near the 

 Utah line. These beds are rich in fine specimens of fossil fishes, includ- 

 ing a skate, which have been described by Professor Cope. They are 

 apparently much less rich in insect and plant life than the Green Eiver 

 beds at Green Eiver City, Wyo. 



For the opportunity of examining and describing* these interesting 

 remains I am indebted to Prof. Joseph Leidy, who received them as a 

 loan from Dr. J. Van A. Carter, of Evanston, Wyo., in whose possession 

 they now are. 



The two specimens are tolerably preserved ; the smaller one presents 

 a dorsal view, and the larger a lateral view, though both have been 

 somewhat distorted, flattened, or compressed by pressure. The length 

 of the smaller specimen from the tip of the rostrum to the end of the 

 telsou is 38°^™ ; of the larger individual, 53™°^. 



The internal layer of the cornea of one eye in the larger individual is 

 preserved and is black, and of the size usual with living species of the 

 genus, but no marks of the facets are visible ', the diameter of the eye 

 through the cornea is 3°^™. 



The first (and smaller) antennre in the small specimen show that they 

 are much as in the species of Cambarus, the two distal joints of the scape 

 appearing, however, rather thicker, probably owing to being flattened by 

 pressure. The flagellum (but one branch is visible) is of the usual 

 length and thickness. Length of the flagellum in the smaller specimen, 

 5'"'» ; in the larger, S™'". 



The second antennse are of the usual size ; the last joint of the scape of 



* A preliminary description of these fossils was published in the Americaii Xaiuralist 

 for March, 1880, vol. xiv, p. 222. 



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