34 Praeger — The Estuarine Clays 



interesting specimen which I found here consisted of a large valve of Cyprtna 

 Islandica, to the interior face of which a full-sized Oyster was adhering, its 

 shell fashioned to the shape of the Cyprina, and the other valve was lying 

 close at hand. This tells of a slow rate of accumulation of the deposit. The 

 Cyprina lived and died, and the valves of its shell in time broke asunder. Then 

 the Oyster came and settled in the untenanted house of its predecessor, and it 

 grew and nourished before the slow rain of fine mud buried both in a quiet 

 grave. Pholas crispata and P. Candida occur frequently ; and a single 

 specimen of Pholas dactylus, new to our Estuarine Clays, was observed. At 

 the base of the bed, where it is quite sandy, there is abundance of Cardium edule 

 — this stratum evidently corresponds with the lower clay of the first section. 

 Below this we come directly upon the red sand ; there is no trace of the peat 

 bed. The sand is nearly twenty feet in thickness, and rests on the red clay. 



It is interesting to compare the sections above described with other sections 

 in the Lagan Estuary which have been examined by local geologists. 

 The beds exposed when Spencer Basin was in course of construction, on the 

 opposite side of the river, which were so thoroughly examined by Mr. Stewart, 

 consisted simply of some twenty feet of Estuarine Clay, which he divides into 

 three well-defined zones : — 



1. Surface clays ; abounding in littoral species. 



2. Zone of Thracia convexa ; characterised by shells which live in five 

 to ten fathoms of water. 



3. Scrobicularia zone ; in which littoral species again predominate. 



The physical and palseontological differences between the two latter were 

 more marked than at Alexandra Dock ; the beds of peat and sand were not 



Borings at King Street, in the centre of the town, under the superintendence 

 of Mr. Wm. Swanston, F.G.S., showed a depth of no less than twenty-eight feet 

 of Estuarine Clay, at the base of which was a layer containing many twigs and 

 hazel nuts. Next came twenty-four feet of fine running sand, which yielded on 

 examination four species of Foraminifera, two of these being the two forms 

 obtained in the red sand at the Dock. Beneath this was fifty feet of very fine 

 red Boulder Clay, in which two Foraminifera were found to occur very 

 sparingly, namely : — Rotalia Beccarii, and Polystomella striato-punctata, the 

 same species which formed the only fossils of the red sand in the Dock sections. 

 The fine clay rested on Boulder Clay, as it usually occurs in our neighbourhood, 

 100 feet in thickness, and abounding in Foraminifera, underlying which were 

 the sandstones of the New Red. 



At Sydenham Railway Station a different state of things may be noticed. 

 "We have only a couple of feet of Estuarine Clay, replete with the shells of 

 species which live between tide-marks, its upper surface being about three feet 

 above high- water mark, or sixteen feet higher than the top of the Estuarine 

 Clay at the Dock. Then comes a foot of yellow sand, at the base of which is 

 a narrow zone crowded with the crumbling remains of littoral species. This 



