On the Paleontology of County Dublin. 163 
Oldhamia antiqua has the appearance of a number of small 
fan-shaped tufts, arranged in an alternating manner, upon a zigzag 
axis. This species is also abundant and well preserved in the 
brown and purple slates of Carrick Mountain, County of Wicklow, 
accompanied there, as at Bray Head, by tracks and burrows of 
animals, which frequently occur in pairs, and resemble those from 
the Cambrian rocks of the Longmynd in Shropshire, named’ by 
Mr. Salter Arenicolites didymus and A. sparsus, species which 
are probably identical. The late Dr. Kinahan believed he had 
detected Oldhamia antigua, accompanied by tracks, in brown 
laminated slates at “Puck’s Rocks,’ near the “ Nose of Howth.” 
The specimen he collected, and presented to the Geological Survey 
Collection, is not, however, so distinct as those from Bray or 
Carrick Mountain. 
Oldhamia vradiata.—The most frequent form resembles a num- 
yer of detached bunches of flattened sea-weed, without any 
connecting axis or stem, covering irregularly the thin laminee of 
the rock, giving it a somewhat star-shaped appearance. This 
species is most abundant on the shore at Bray and Greystones 
Co. Wicklow. 
Histioderma Hibernica is a fossil from the same rocks at Bray, 
described by Dr. Kinahan* as “the cast of a tentacled cephalo- 
branchiate sea-worm, not very dissimilar from the common lug- 
worm (Avenicola) of our present seas.” This fossil is of consi- 
derable size; it may be seen occurring as mounds on the surface 
of a large calcareous bed on the shore, a little south of the Peri- 
winkle Rocks. These mound-like protuberances are about one 
inch and a-half in diameter, with a central depression from which 
proceeds a tubular opening of about half-an-inch in diameter, 
passing vertically through the rock from two to four inches, or 
even more, sometimes in a tortuous or curved manner. ‘These 
fossils are entirely confined to Irish strata, excepting the double 
markings, supposed to be the burrows of sea-worms (annelidan), 
named by Mr. Salter Avenicolites didymus and ‘A. sparsus. 
The Oldhania and Histioderma have not been detected in the 
Cambrian rocks of the Longmynds, or those of North Wales. 
Haughtonia pecila, described by Dr. Kinahan, from red gritty 
beds,. Periwinkle rocks, Bray Point;:as.an aggregation of the 
* Journal of the Geological Society of Dublin, vol. viii., p. 71. 
