A LOWER CAMBRIAN EDRIOASTERID 



Stromatocystites zvalcotti 



By Charlks Schuchert 

 (With i Plate) 



In 1910, while the writer was studyin.q' the strati.^raphy of western 

 Newfoundland, he Avas much surprised to find in the Lower Cam- 

 brian a number of cystids that seemed to be related to the edrio- 

 asterids. These and other Lower Cambrian fossils were collected 

 for the United States National Museum, and the study of the edrio- 

 asterids was kindly turned over to the writer by the Secretary of the 

 Smithsonian Institution. In admiration of the long-continued and 

 excellent work which the latter has done on the Cambrian, in the 

 midst of seemingly endless administrative duties, the new species 

 herein described is given the name Stromatocystites zvalcotti. 



It was thought at first that these fossils represent a new genus, but 

 after seeing two specimens of Stromatocystites pentangularis from 

 the Middle Cambrian of Bohemia, which are in the Peabody 

 Museum collection in Yale University, it became clear that the New- 

 foundland form is a species of Stromatocystites. Accordingly, we 

 will begin with a definition of that genus, in the main as given by 

 Pompeckj/ 



Stromatocystites { redefined ) 



Text fig. I E 



This is a flat and depressed cystid, and it is this spread-out con- 

 dition that has suggested the name. Theca free, imstalked, sub- 

 pentagonal in outline, and composed of numerous comparatively 

 large, non-imbricating, and usually five- and six-sided plates. In a 

 theca 35 nmi. in diameter there may be t.ooo plates. Upper surface 

 convex, lower one concave. Ossicles of the upper side bearing, 

 along each angulation of their margins, usually 2 to 3 diplopore 

 depressions that extend across the sutures of adjoining plates ; on the 



*J. F. Pompeckj. Jahrb. d. k. k. Geo!. Reiclis., Vienna, 45, 1895, pp. 505-508, 

 pi. 13, figs. 1-6. Also see F. A. Bather, Treatise on Zoology, Part III, 

 Echinoderma, p. 206, fig. i. 



Smithsonian Miscellaneous Collections, Vol. 70, No. 1 



