Dr. J. R. KiNAHAN on the Genus Oldhamia. 561 



which comes as close to this species as Sertiilaria argmtea approximates Oldha- 

 mia antiqua, none of the Sertularidre growing in that regular stellariform man- 

 ner except one or two creeping species ; but in that case some traces of the 

 body to wliich the polypidom was attached ought to have been found ; unless, 

 indeed, this is a species growing free at the surface of the water, which appears 

 a most improbable supposition. There are, I am aware, a few species of creep- 

 ing Polyzoa, which have a mode of growth somewhat resembling 0. radiata, 

 but it appears to me that Old. antiqua must have been a Sertularian, and it is, 

 therefore, more probable tliat Oldhamia radiata was so also. 



There remains now but to sum up in brief the points established in the 

 review of this genus, which are: — 



In the schist rocks of the Irish Cambrians, beds occur of considerable 

 thickness, traceable continuously for many hundreds of yards, which are com- 

 posed almost entirely of the polypidoms of an extinct Sertularian which occurs 

 in connexion with other extinct aquatic types, such as Annellids, Mollusca (?), 

 and Asteroid Polyps ( ?). 



That these fossils, judging from the almost absolute identity of one of them 

 with the polypidom of a living Sertularian type, are more probably the polypi- 

 doms of extinct Ilydrozoa than cosncecia of Polyzoa. And — 



That judging from their state of preservation, their mode of occurrence in 

 enormous masses, and the nature of the rocks in which they occur, they were 

 originally the inhabitants of a comparatively still sea, and depo.sited by a gentle 

 current on the shores of a shallow sandy bay. 



