A BARE CEETACEOUS SEA URCHIN, SCUTELLASTER 

 CRETACEUS CRAGIN 



By John B. Reeside, Jr., 



, Of the United States Geological Surveij. 



The genus ScuteUaster was instituted in 1895 by F, W. Ci'agin ^ 

 for the reception of a specimen " from the arenaceous shale of the 

 Fox Hills division of the Cretaceous, on the east slope of Shook's 

 Run, on Piatt avenue, Colorado Springs, Colorado." The type was 

 not figured and the description given indicated that it was rather 

 imperfect. Clarke^ in 1915 in his monograph of the Mesozoic 

 Echinodermata of the United States reserved judgment on both 

 genus and species until better, material could be found and quoted 

 a statement by Cragin that the latter had come to doubt the validity 

 of the genus ScuteUaster. No other specimens have been found to 

 date, however, and both the extreme scarcity of echinoids in the 

 Cretaceous of the Interior Province and the unusual character of 

 the species in question warrant further description in spite of the 

 imperfect material. The type was originally a part of the Cragin 

 collection of the museum of geology at Colorado College, Colorado 

 Springs, Colo., but is now in the United States National Museum 

 (Cat. No. 32702). The horizon of the specimen is now believed to 

 be in the top of the Pierre shale rather than the Fox Hills sandstone. 



Cragin's original description is as follows : 



SCUTELLASTER, new genus 



Glypeastrid lax'ge, combining the flattisli-convex, or diseoidal, test of Scutella 

 with the pentagonal outline of Clypeaster; disc without loopholes or any 

 emarginations other than shallow convexities; ambulacral petals closed, or 

 nearly so. 



SCUTELLASTER CRETACEUS, new species 



Plate 1, figs. 1 and 2 



Test as large as that of a large Scutella, or that of one of the more moderate- 

 sized species of Clypeaster, obtusely pentagonal, its height apparently about 

 equal to, or not more than, one-tenth of its length; ambulacral petals of 



* Cragin,. F. W., A new Cretaceous genus of Clypeastridae : American Geologist, vol. 15, 

 pp. 90-91, 1895. 



" Clark, W. B., and Twitchell, M. W., The Mesozoic and Cenozoic E)chinoderroata of the 

 United States : U. S. Geol. Sui-vey Men. 54, p. 67, 1915. 



No. 2557.— PROCEED! NGS U. S. NATIONAL MUSEUM, VOL. 66, ART. 20 

 9114—24 I 



