NOTE ON CORONURA ASPECTANS, CONRAD (sp.), 

 The Asaphus diurus. Green. 



By J. M. Clarke. 



Communicated to the State Geologist December, 1890. 



The species Asaphus aspectans was founded by Conrad in 1841* upon 

 a fragment of a cephalon consisting of a free cheek, retaining the 

 lensar surface of the ocular node. This specimen was from the Cor- 

 niferouB limestone at Schoharie, N. T., and was characterized by the 

 great elevation of the eye (represented by Conrad as almost semi- 

 cylindrical), the broad and entire marginal border and the coarse 

 tuberculation of the surface. Until the publication of Volume VII of 

 the Jralseontology of New York (1888) the name had not been regarded 

 of much value, from the very fact of the obscurity and apparent insuf- 

 ficiency of the original specimen. Professor Hall had reproduced in 

 the Fifteenth Annual Report on the State Cabinet of Natural History* 

 (p. 88, 1862) Conrad's brief diagnosis and his figure, and in a short 

 note of observations refers to a second specimen, curiously enough 

 almost the duplicate of the original ; both of these specimens, left 

 free cheeks, are figured on plate 13 of the volume of the Palaeontology 

 of New York referred to. 



In the study of the tipper Helderberg trilobites made in the 

 preparation of this work it became evident that the large pygidia, 

 not infrequent at some outcrops of the Corniferous limestone, 

 characterized by rows of conspicuous marginal spines and a 

 crescentic posterior extremity, and which were currently referred 

 to the species described by Professor Hall as Dalmania Helena, 

 or that by Mr Meek as Dalmania Ohioensis, had possessed a 

 cephalon, the eye and cheek of which must have closely conformed 

 to that described as Asaphus aspectans. The evidence, however, that 

 these different parts represented but a single species was rather 

 slender, notwithstanding the fact that so much confidence was there 

 felt of this probability that all these pygidia were referred to Conrad's 

 species. The argument was on this wise: Professor Hall's D. -Sefena 

 was based upon a poorly preserved pygidium from the Falls of the 



* Fifth Annual Report on the Palaeontology of the State of New York, p. 49, plate, fig. 9. 



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