394 . Baily— Cambrian Rocks and Fossils. 
on the same surface of this thin bed are horizontal tracks of various 
sizes and burrows of Arenicolites, with double openings resembling 
A. didyma, represented on the same figure at 6.* 
Varieties of this species occasionally accompany the ordinary 
form, particularly in the shales of Carrick Mountain. In some of 
these, the fans of branchlets are more closely arranged upon the 
axis, and are more wavy and intermittent, the fasciculi being 
denser: this is the variety (before alluded to) which was believed 
by Dr. Kinahan to constitute a third species, aud to which he applied 
Fic. 4.—OLDHAMIA ANTIQUA, FORBES, CAMBRIAN, CARRICK MOUNTAIN, COUNTY OF WICKLOW. 
a, Ordinary form at this locality. 6. Var. (0. discreta, Kinahan), 
c. Hlongated variety. All natural size. 
the name of O.discreta (fig. 5, a). Another and more attenuated 
form is generally present on the opposite side of the same slabs : in 
this, the fans of branchlets are less dense, and appear to be drawn 
out of shape, probably by the effects of cleavage (fig. 5, 6). The 
specimens of Oldhamia antiqua from this locality occur in brown 
and buff-coloured shales, easily separating and more argillaceous 
than those of Bray. 
The localities for this species are various stations in the rocks of 
Bray Head and Carrick Mountain, county of Wicklow, and Howth, 
county of Dublin, in beds generally distinct from those containing 
O. radiata ; although Dr. Kinahan remarks that scattered forms of 
O. antigua sometimes occur, though rarely, in the beds of O. radiata. 
The second species, Oldhamia radiata, is the most abundant one 
* T have noticed similar double markings occurring on some of the fine-grained 
laminated grits at Carrick Mountain. From the same locality was also procured a 
large worm-cast resembling those of the Histioderma.—W. H. B. 
