at the New Alexandra Dock , Belfast. 31 
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 , JRissoa striata , Melampus bidentatus , Utriculus 
obtusus, Cardium nodosum ; and the following are new to the deposits : — Capulus 
Hungarians, Helcion pellucidum, Cylichna cylindracea , Utriculus mammillatus , 
Anomia aculeata , Echinus sphcera. Beds occur of Ostrea and Eecten 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 Eholas 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 ar e:—Zittorina litorear, 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 . ° 
