•556 Dr. J. R. Kinahan on the Genus Oldhamia. 



Oldhamia antiqua (Forbes). Figs. 1, 2, 6, 7. 



Polypidora cauliferous ; stem percurrent, sub-flexuous, filiform ; furnished 

 with short fan-shaped branchlets, arranged at regular intervals ; branchlets 

 straight, very slightly sub-flexuous, few in number ; cells biserial and alternate. 

 Locality: schist rocks, Bray, Graystones, Carrickmount, county of Wicklow ; 

 Howth, county of Dublin. 



Two varieties of this are figured: Figs. 1, 2, 6, represent the ordinary form ; 

 the fans are far apart and distinct, and their secondary axes few in number, 

 somewhat dichotomous ; the cells which constitute them well marked. 



The second variety (Fig. 7) is often mistaken for a 

 state of Old. radiata, but is readily distinguished by the 

 presence of the central axis. In this the fans are closely 

 crowded, their terminating cells broader than the basal 

 ones, so that in some specimens these are quite club- 

 shaped ; the secondary axes are numerous, much more 

 so than in the other form. All the specimens figured are 

 from Bray Head. ,, , .„, ,■ m 



*' rig. 7. Oldltamia a>ttiqim(^;) 



The specimens from Howth differ in some respects exhibiting closely crowded fas- 

 irom those at Bray, and may be a distinct form. The '^'"^"''' ^""^ -"merous branch- 

 secondary axes are broader, markedly so towards their 



tips ; the fans few rayed, far apart, and patent. Fine specimens may be seen 

 in the Geological Survey Collection at the Museum of Irish Industry. The 

 same foi-ni occurs at Carrickmount Eeilly, county of Wicklow. The speci- 

 mens of this species which occur scattered through the red shale at Bray are 

 much finer in texture than any of the varieties described. 



Among the specimens collected by the ofiicers of the Survey, some years 

 ago, at Carrickmount, county of Wicklow, are several, occurring in a yellow 

 schist, which are so different from any of the varieties of Old. antiqua, that I 

 propose to describe it as specifically distinct, provisionally, as follows: — 



Oldhamia discreta (n. s.). 

 Polypidom cauliferous ; stem percurrent, filiform, furnished with densely 

 crowded alternate fans of branchlets ; branchlets flexuous, dichotomous, very 

 numerous, filiform ; cells biserial, alternate, strongly marked. 



