Oldhamia. 229 



Prof. H. A. Nicholson in his Palaeontology classes Old- 

 hamia with the Hydrozoa, but stated that its nature was 

 uncertain. 



This fossil occurs in the finer layers of the green and 

 purple grits of Lower Cambrian age at Bray Head in 

 Ireland, where the fronds are in great abundance, matted 

 together and spread over the surface of the finer layers. 

 The species which occur here are 0. antiqua and 0. radiata. 

 Though Goeppert refers them to different genera, some 

 later observers think they are all of the one species, but in 

 different attitudes of preservation. Radiata appears to be 

 the form first described, and so would be the type of the 

 genus. The form figured by Nicholson (after Salter) as 

 0. antiqua is not of the same type as that which Zittel 

 figures under the same name. They appear to belong to 

 different species, and perhaps Nicholson's figure represents 

 the type radiata. 



Mr. Etheridge says that " Oldhamia must have had a 

 calcareous or semi-calcareous structure to have been preserved 

 at all," and when one notices how deeply the mould of 

 this fossil is indented on the surface of the slate, this claim 

 seems well founded. Mr. Etheridge also remarks of 

 Goeppert " that he does not seem to have perceived that 

 the hard filament must needs have been connected by a 

 membrane, not quite destroyed, and that the frond must 

 have been sufiiciently hard to impress the sandy deposit 

 in which they are imbedded." We (R Etheridge) place 

 these singular organisms provisionally in the class 

 Hydrozoa, believing them to have close af&nities with the 

 Sertulariidee, and belong to that group rather than the 

 calcareous corallines. He also adds that 0. antiqua is 

 rarer than the other, but Prof. Nicholson says that 0. 

 antiqua is the commoner species. 



There seems to be considerable uncertainty still as to 

 the exact horizon in the Cambrian at which the original 

 Oldhamia was found. At first the fossil was referred to 



