at the New Alexandra Dock, Belfast. 3 1 



3. Immediately below the yellow sand, the line of demarcation being 

 remarkably sharp and well defined, is the Estuarine Clay proper. This forma- 

 tion, as Mr. Stewart has shown,* consists at Belfast of two beds which were 

 laid down under widely different circumstances — an upper one, which was 

 deposited in some thirty or forty feet of water at least, and a lower one, which 

 is of a littoral character. The upper bed consists of very fine homogeneous blue 

 clay, and is here about six feet thick. It is remarkably rich in shells, both large 

 and small, many of which do not now exist in our waters, and they are for the most 

 part in a beautiful state of preservation. Thracia convexa, Lucinopsis undata, Car- 

 dium echinatum, Scrobicularia alba, Ostrea hippopus, Acera bullata, are abundant, 

 and characteristic of the deposit. Among many rare fossils obtained from this bed 

 may be mentioned : — Actceon tornatilis, Cyprcea Europcea, Cardium Norvegicum, 

 Tellina tenuis. Not hitherto recorded from the Belfast bed are: — Aclis 

 supranitida, Trochus umbilicatus, Rissoa striata, Melampus bidentatus, Utriculus 

 obtusus, Cardium nodosum ; and the folloM'ing are new to the deposits : — Capulus 

 Sungaricus, Helcion pellucidum, Cylichna eylindracea, Utriculus mammillalus, 

 Anomia aculeata, Echinus sphozra. Beds occur of Ostrea and Pecten maximus, 

 both of which attain a large size ; Scrobicularia piperata is almost unknown. 

 Near the top of the deposit a shell layer occurred, made up almost entirely of 

 Scrobicularia alba and the spines of two Echinoderms — Amphidotus cordatus and 

 Echinus miliaris. It is to be noted that the former, which now occurs around 

 our coasts only in sandy bays, here lived abundantly on a bottom entirely 

 muddy. 



At the base of the bed just described is a narrow zone in which the boring 

 shells, Pholas crispata and Pholas Candida, occur in profusion ; this layer was 

 also observed by Mr. Stewart on the County Antrim side of the Lagan. The 

 shells are found in a horizontal bed, all in the position in which they lived. P. 

 crispata is of very large size, twice the size which it now attains on the North 

 of Ireland coasts — one specimen measured five inches in breadth by seven and 

 a half in girth. The occurrence of these shells between the overlying deep- 

 water clay and the underlying littoral deposit is of great interest, ' ' and their 

 appearance," says Mr. Stewart, "is the first intimation of the subsidence then 

 commenced." 



4. "We now come to the lower clay, which had a depth of between six and 

 seven feet. It is of a more sandy nature, and has a yellower colour than the 

 upper bed, and is full of the remains of the Grass "Wrack, Zostera marina, which 

 furnishes further proof, if such were needed, that this is a shallow water deposit. 

 But the contained fossils testify this conclusively. Scrobicularia piperata is the 

 leading shell of this bed, occurring all through in extraordinary profusion ; an 

 essentially littoral species, which is now quite extinct on our northern coasts. 

 Other characteristic fossils are: — Littorina litorea, Cardium edule, Tapes 

 decussatus. The latter attains by no means so large a size as it does in the bed 



* Stewart— "Latest fluctuations of the sea-level on our own coasts," Eighth Annual 

 Report, Belfast Naturalists' Field Club, 1871. 



