A NEW MIDDLE CAMBRIAN MEROSTOME CRUSTACEAN 



By Charles Elmer Resser 



Curator, Division of StratigrapMo Paleontology, United States National Museum 



Frank Beckwith, of Delta, Utah, recently sent to the United States 

 National Museum for identification a photograph of a fossil collected 

 by Emory J. John, of Clear Lake, Utah, in the banded argillaceous 

 limestones of the Marjmn formation in Weeks Canyon, House 

 Range, Utah, stating that if the animal represented was not a 

 trilobite, or if it was rare, he would be pleased to present it to the 

 National Museum. Since this is the first example of a merostome 

 from either the horizon or geographic region, it is, naturally, a rare 

 form, and Mr. Beckwith's generous offer was accepted at once. 



In order to check my interpretations, I sent photographs of this 

 interesting fossil to Dr. Rudolf Ruedemann at Albany, N. Y., and to 

 Gilbert O. Raasch at Madison, Wis., the only geologists known to me 

 who are specializing in this group. It is interesting to note that their 

 opinions agreed quite closely and fully confirmed my interpretations. 



The first known Cambrian merostome was discovered many years 

 ago in Wisconsin and described in 1863 by Hall as Aglaspis bar- 

 randei} A second species from the same general region was described 

 by Whitfield in 1882 as A. eatoni.^ Since that time the Upper Cam- 

 brian beds of Wisconsin have produced many of these crustaceans, 

 descriptions of which by Raasch are about to appear. He has 

 founded nine genera, seven of which contain one or more species 

 based on specimens preserving the entire test. In addition to these 

 and the eurypterid Strabops thacheri Beecher,^ from the Upper 

 Cambrian of Missouri, we have merostomes from Middle Cambrian 

 beds at several places, particularly from the Burgess shale (Molaria; 

 Hahelia, Emeraldella, Sidneyia., and AmieUa). Finally, the Lower 

 Cambrian has furnished several forms, such as Amiella prisca Man- 



1 letli Ann. Rep. New ^ork State Cab. Nat. Hist., p. 181, pi. 4, figs. 7-16, 18G3. 

 ''Geology of Wisconsin, Survey of 187»-1879, vol. 4, pt. 3, p. 192, pi. 10, fig. 11, 1882. 

 «Amer. Journ. Sci., vol. 12, p. 364, pi. 7, 1901. 



No. 2899.— Proceedings U. S. National Museum. Vol. 79. Art. 33 



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