HARD WICKE'S SCIENCE- G OSS I P. 



1S1 



to a height of 1,659 feet, and the Little Sugarloaf, 

 about two and a half miles south of Bray, to 1, 120 feet. 

 This Cambrian district of North Wicklow, com- 

 mencing somewhat north of Bray, and including part 

 of the river Dargle, extends to near Wicklow, a length 



of seventeen miles, spreading out to seven or eight 

 miles. 



At certain places in the district this formation 

 contains a very distinct, though specifically small, 

 assemblage of fossils. Two species of Oldhamia 



Fig. 124. Oldhamia radiata 



Fig. 125. Tracks and burrows of Arenicolites sparstts, copied from 

 Baily's " British Fossils." 



Fig. 126. Burrows of Arenicolites didymus. 



Fig. 128. Extremity of tube of Histiodcrma 

 Hibernicum. 



(named after Professor Oldham), 0. antiqua 

 and 0. radiata, have been described and 

 named by the late Professor E. Forbes ; they 

 are confined to Irish strata, and occur in 

 considerable abundance at several places in 

 the rocks of Bray Head; at Graystones, on 

 the coast three miles further south ; and at 

 Carrick Mountain (1,260 feet high), north of 

 Rathdrum. These fossils were believed, by 

 Professor Forbes and the late Professor J. R. 

 Kinahan, M.D., to be allied to Sertularian zoophytes; 

 other scientific observers consider them to have been 

 plants, probably marine algre, allied to lime-secreting 

 nullipores. 



Accompanying the Oldhamia are evident remains 

 of marine annelids, which burrowed in the sand of 

 that period, producing tracks penetrating the beds 

 in a vertical and horizontal direction ; they correspond 

 with those described by the late Mr. Salter from 

 the Longmynds as Arenicolites didymus, and A. 

 sparsus (probably identical species) ; some of them 

 occur in pairs of double openings, which pass 



