Vol. 56.] ICHNIUM AND OLDHAMIA. 273 



16. Fossils in the Oxford University Museum. — III. Icsnium 



Wattsii, a Worm-track from the Slates of Bray Head : with 



Observations on the Genus Oldhamia. By Prof. W. J. Sollas, 



M.A., LL.D., D.Sc, F.B.S., Y.P.G.S. (Read January 24th, 



1900.) 



[Plates XVII-XIX.] 



The abundant literature which has been evoked by certain curious 

 markings in the ancient rocks of Leinster since they were discovered 

 by Oldham in 18-14 (l) 1 is illustrative of the interest aroused by an 

 unsolved problem. Its solution would appear to be still incomplete, 

 and the present communication, while adding to our knowledge, at 

 the same time adds to the facts to be explained. Of late years 

 the subject has acquired additional importance, since the recognition 

 of specifically identical markings in similar rocks of other parts of 

 Europe (12, 13, 14, 21) and America (23) has led some geologists 

 to regard them as guides to the ' identification of strata/ Without 

 expressing any opinion as to their value for this purpose, it may 

 yet be noticed as a very remarkable circumstance that hitherto 

 Oldhamia has not been recorded from younger rocks than the 

 Lower Palaeozoic ; according to most writers, indeed, it is confined 

 to the Cambrian System. Thus in the Ardennes Oldhamia antiqua 

 is found associated with Nereites cambrensis in the greyish-green 

 phyllades of Fumay; and in the Devillo-Bevinian of Stavelofc 0. 

 radiata occurs together with an Agnostus and Arenicolites didymus. 

 In Brabant 0. radiata is met with in the middle member of the series 

 of phyllades and quartzites which are there supposed to represent 

 the Cambrian. At one time De Lapparent 2 cited Oldhamia as 

 present in Ordovician strata ; his words are as follows : — i A la 

 base [of the Silurian System] s'observent a Boutoury les couches a 

 Bellerojjhon CEhlerti et a Didymograptus dont les assises inferieures 

 offrent le melange d ! 'Agnostus et Oldhamia avec Megalaspis, Caly- 

 mene, lllamus (c'est l'horizon d'Arenig).' In the latest edition of 

 the ' Traitc,' the statement is repeated ; but the horizon is given as 

 that of Ceratopyge (p. 805). 



Barrois (23) has described a species of Oldhamia from Palaeozoic 

 schists in the Pyrenees ; the locality is given as the ravine of 

 Montmedan-Maju, near Jurvielle (Haute Garonne). The genus is 

 also probably represented in the Cambrian rocks of Norway; 

 Kjerulf's statements on this point are, however, very guarded, and 

 unaccompanied either by figures or descriptions. Thus he speaks 

 (12) of ' impressions which strongly recall those of Oldhamia^ and 

 of ' traces of sand-worms and Oldhamia ' as occurring in association 

 with the ' Blue Quartz.' 



1 The numbers in parentheses throughout this paper refer to the Bibliography 

 on p. 284. 



2 ' Traite de Geologie ' vol. i (1893) p. 780. 



