254 • The Irish Naturalist, [Oct., 



OLDHAMIA IN AMERICA. 



BY PROF. GRENVII.I.E A. J. COI.K, M.R.I.A., F.G.S. 



Oldha7?iia, the obscure ridge-like and radiating marking 

 that occurs in the shales of the Bray series, has made the 

 county of Wicklow famous among geologists throughout the 

 world. Continental text-books have figured these problematic 

 objects, adding, perhaps, even greater firmness to their out- 

 lines, and greater symmetry to the disposition of their rays. 

 The handsome specimens in the Survey collection in the 

 Dublin Museum are, indeed, enough to stimulate curiosity, 

 even if they are disappointing to those who look for distinct 

 organic structure. The vSupporters of the organic view of 

 Oldhaviia will, however, receive much encouragement from 

 the discovery of similar objects in America iji strata of Cavit)rian 

 or Lower Ordovician age. Mr. C D. Walcott, Director of the 

 U. S. Geological Survey, has published {Proc. U, S. Natio7ial 

 Museum, vol. xvii., p. 313) a valuable description of Oldhamia 

 occidens Walcott, from shales near Troy, New York State. I 

 am indebted to the author for kindly sending me a copy of a 

 paper not easily accessible. 



Mr. Walcott throws doubt on Hall's Oldhamia friUicosa, 

 from the Trenton Limestone (Upper Ordovician) of Wisconsin, 

 but accepts Lapworth's determination of an Oldha^nia, species 

 uncertain, from the Cambrian slates of Farnham, in the 

 province of Quebec. 



The specimens on which the new record are based were 

 sent, with various indeterminable tracks and impressions, by 

 Mr. T. N. Dale to his chief in 1893. Oldhamia occidens is 

 placed under the sub-genus Mtirchisonites-, proposed by Brady 

 for O. antiqua in 1865 ; but it differs from that species by the 

 fact that each fan-like tuft springs serially from the summit 

 of that preceding it — or, as appears from the figure, from some 

 point slightly behind the summit, so that the "fans" are 

 grouped along a straight line, the broad edge of one just over- 

 lapping on the point of origin of that following it. 



The description of the beds, which are " post Lower Cam- 

 brian and pre-Trenton," reminds one very strikingly of those 

 of Bray. 



