Baily— Cambrian Rocks and Fossils. 395 
in the rocks of Bray Head ; and at Greystones, on the coast, four 
miles farther south, it occurs in a precisely similar rock to that 
called the Periwinkle Rock of Bray Head, and was the only species 
observed by me at that locality. Dr. Kinahan has evidently mis- 
taken it for O. antiqua, the figures he gives under that name in the 
paper before quoted (figs. 9 and 10, p. 559) being unquestionably 
those of O. radiata. It has not been observed at Howth, Carrick 
Mountain, or any other locality than the two I have mentioned. 
The most ordinary form is that shown in the woodcut, fig. 3, a, p. 391. 
Fic. 5.—OLDHAMIA RADIATA, FORBES, SHOWING SUCCESSIVE LAYERS. 
a. Ordinary form. 6, Plumose variety. 
Cambrian (green grit) Periwinkle Rocks, Bray Head, County of Wicklow. 
The general appearance presented by this species is that of a 
stellariform mass of filaments or branchlets, of variable length, which 
often divide into two, becoming wavy and intermittent, or jointed, 
all the separate tufts radiating from a central point or axis. 
The star-like form is more or less complete in consequence of the 
variable length of the branchlets: sometimes one or more of these 
are very much elongated, giving the fossil a more plumose appear- 
ance, as shown on fig. 3, at 3d. 
The principal, and, I believe, only localities for this species, are 
those of Bray Head and Greystones, county of Wicklow, at both of 
which places it is met with in the greatest profusion, occurring 
