Mactra solida, Linn., var. elliptica. It is doubtful whether Grainger's note, "occurred pretty often in the sandy deposits," refers to the estuarine clay beds. Stewart omits the note in his enumeration; nor did this variety occur to him in his investigations. A single valve was found in the lower clay at Alexandra Dock, which is my only note of it.

M. subtruncata, Da Costa. Was present in most of the deposits, usually of small size.

Lutraria elliptica, Lamarck.

Its occurrence in the Belfast bed has been noticed by Hyndman and all subsequent writers. At Alexandra Dock the specimens were in every stage of growth, and the rich, golden-brown epidermis beautifully preserved. At the north end of the works a large colony occurred, the shells all in the natural position, and occupying one zone of the clay in profusion. Magheramorne was the only other station at which it was found; there the specimens were small.

*L. oblonga, Chemnitz. "Found in a recent deposit of blue clay excavated for a dock at Belfast, Dr. William M'Gee."-Thompson. The dock referred to is Prince's Dock. "A remarkably fine specimen of this now absent species occurred to the late James Lemon, Esq."-Grainger. It is rarer still in the district in a recent state.

Scrobicularia alba, Wood. A characteristic shell of the upper estuarine clay. In the deposits of Lough Foyle, Magheramorne, Belfast, and Downpatrick, it was present in great profusion. At Larne, Newtownards, Kircubbin, Newcastle, and Greenore, it occurred in sparing numbers. It inhabits the adjoining waters in 6 to 20 fathoms.

*S. tenuis, Montagu. Is recorded by Bell from the Belfast deposit.

S. piperata, Bellonius. The typical shell of the lower or Scrobicularia clay, in which it is usually present in enormous numbers. At every point where this bed was examined in the Belfast estuarine area, by Hyndman, Grainger, Stewart, and the writer, it was present in the utmost profusion, from the first lock on the Lagan Canal to Kilroot, and from Millfield to Connswater. At

Newcastle, also, it is most abundant. Occurs in varying numbers in the Lough Foyle and Larne Lough beds, at the Bann, and at Greenore and Dundalk. It is absent from the Strangford Lough deposits, and from the Thracia clays of Belfast and Magheramorne. The specimens are often of large size; Grainger mentions specimens 1 by 2 inches; and I have before me one from Larne pottery measuring 13 by 24 inches. Like Tapes decussatus, which often rivals it in abundance in the lower clay, this mollusk has now completely deserted the habitat which it previously almost monopolised. Its nearest certain present stations are the same as those of Tapes-Lough Swilly on the north, and Carlingford Lough on the south. Southward of Carlingford Lough S. piperata still abounds.

*Solecurtus antiquatus, Pulteney. "A single rather fine example of this scarce species was obtained in the (Belfast) clay by E. Aiken, Esq., of Dublin."-Grainger. It is marked in Bell's list as having occurred to him at Magheramorne.

*Ceratisolen legumen, Linn. Noted by Bell from the Belfast bed. Very rare in the district at the present day.

Solen pellucidus, Pennant. Is of frequent occurrence in the Belfast Thracia clay, as noted by several writers. Limavady Junction was the only other station at which it occurred to me; there it was very rare. Stewart records it from Magheramorne.

S. ensis, Linn. Not common, but occurs at Eglinton, Larne, Magheramorne, and Belfast.

S. vagina, Linn. Noted in all the lists of the shells of the Belfast clays as of frequent occurrence. At Alexandra Dock fine and perfect specimens occurred, and I have it also noted from Eglinton, Magheramorne, and Holywood. This species is now extremely rare on the North of Ireland coasts, and has not been taken in a live state; while S. siliqua, which is absent from the estuarine deposits, flourishes abundantly in our waters.

Thracia papyracea, Poli. Frequent in the Belfast deep-water clays, and occurred sparingly at Limavady Junction, Bann, and Larne.

var. villosiuscula was noted by Stewart as frequent at Belfast. It occurred to me in the Larne clay.

T. pubescens, Pulteney. One specimen was obtained by Grainger in the Belfast bed. The writer found a full-sized valve in the Magheramorne deposit.

T. convexa, W. Wood. Selected by Stewart as the typical shell of the upper or deep-water clay. This applies excellently to Belfast, where fine specimens occur in that bed in profusion. Elsewhere

it is rare; a few valves at Limavady Junction and Magheramorne being its only occurrence to me. A specimen in Canon Grainger's collection measures 3 inches in breadth.

T. distorta, Montagu.

Corbula gibba, Olivi.

Several large valves at Magheramorne.

Abundant in many of the deep-water clays, as the Lough Foyle beds, Magheramorne, Belfast, and Downpatrick. Specimens usually small and thin.

In

Mya arenaria, Linn. Rare, and conspicuously absent from the Scrobicularia clays, where it would naturally be expected to occur. the surface clays at Alexandra Dock it was present in thousands, but can hardly be considered as fossil there. Of occasional occurrence in the Thracia clays. Very common at the present day.

M. truncata, Linn. More common than the last species, being abundant in the deep-water clays of Eglinton, Limavady Junction, and Alexandra Dock, and more rarely at Magheramorne, West Bank, and Holywood. The Belfast specimens were of fine dimensions, measuring up to 21 by 34 inches.

M. binghami, Turton. Noted by Stewart as at Magheramorne, very rare. To the writer it occurred frequently there, and a few valves were also found in the West Bank material.

*Panopea plicata, Montagu.

"Plentiful at Belfast in one narrow zone of the clay bed. Not yet found living on the Irish coasts". Stewart. Jeffreys (Brit. Conch. Supplement) also notes it from Belfast, on Bell's authority, and Bell records it from Magheramorne also.

Saxicava rugosa, Linn. Frequent at Magheramorne. Rare at Alexandra Dock, West Bank, and Kircubbin. Specimens usually small. var. arctica. A few valves are recorded by Grainger from the Belfast bed. One fine and complete specimen occurred to me at Alexandra Dock.

*Gastrochæna dubia, Pennant. "Two portions of the curious flask-like tubes of this species were found in the deposits "-Grainger. Has

not been found subsequently either at Belfast or elsewhere, and does not now inhabit the North of Ireland.

Pholas dactylus, Linn. One specimen at Alexandra Dock, and a fragment at Limavady Junction. A large single valve in the Belfast Museum is labelled as found in the Belfast estuarine clay by William Thompson.

P. candida, Linn. The most abundant Pholad of the estuarine clays. The occurrence in the Belfast deposits of a zone between the Thracia and Scrobicularia clays, characterized by an abundance of this and the following species, which did not occur in either the overlying or underlying bed, has been already alluded to. At Alexandra Dock this zone yielded the present species in profusion. At West Bank, at almost exactly the same level (21 feet below high-water mark), and there only, the clay was charged with this shell; but here the Thracia bed was very thick, and underlay the Pholad zone for a considerable depth. This species is common in the Lough Foyle beds, and a few valves were found in the Newcastle clay.

P. crispata, Linn. Long known from the Belfast deposit, where it attains extraordinary dimensions, as already stated. Stewart noted that it was found only in the Pholad zone, at the base of the Thracia clay. At Alexandra Dock, where alone it occurred to the writer, the same remark applies. The dimensions attained by these examples are often 4 inches in breadth by 24 inches in length, and 8 inches in girth. The specimens now obtained living in the lough, which burrow in sandstone, shale, and Boulder clay, near low-water mark, average 24 inches long by 14 in breadth; so the bulk of these estuarine clay giants was eight times that of the living examples. It should be noted, however, that single valves, almost as large as those of the clays, are washed up by the tide at both Cultra and Ballyholme, and probably in deep deposits of mud in the quiet waters below low-water mark, the species still flourishes as it did in the estuarine deposits.

Teredo norvegica, Spengler. Its occurrence in the Belfast deposits, in which it is widely but sparingly distributed, has been noticed by every observer since the time of Thompson. It did not occur in any of the other deposits examined by the writer.

GASTROPODA.

Patella vulgata, Linn. Rare, as should be expected from the absence of stones or rocks, but occurs in the clays at Belfast, Magheramorne, Larne, Greenore, and Kircubbin. Specimens small.

var. depressa accompanied the typical form in the gravel underlying the clay at Larne.

Helcion pellucidum, Linn. Was frequent in the clay at Larne pottery, and a few examples were found at Alexandra Dock and Kircubbin.

var. lævis occurred sparingly in the Larne beds.

Tectura virginea, Müller. Stewart has recorded this species from Belfast. The writer found it frequently at Larne and Kircubbin, and very rarely at Downpatrick.

Ergmainula fissura, Linn. A single example in the Kircubbin clay.

Fissurella græca, Linn. Common, but very small in the Kircubbin bed; rare at Larne, Belfast, and Downpatrick.

Capulus hungaricus, Linn.

Alexandra Dock.

One worn shell in the Thracia clay at

Cyclostrema nitens, Philippi. This tiny shell was noted by Stewart as common at Magheramorne. To me it occurred only sparingly there, as also at Limavady Junction, Larne, and Downpatrick. Bell also notes it from Belfast.

* Lacuna crassior, Montagu. Recorded by Bell from Magheramorne. L. divaricata, Fabricius. Occurred in almost every bed examined, often of fine size. An examination of Canon Grainger's specimens shows that this was the species recorded in each of his lists as L. crassior. The author concurs with me in this correction. var. quadrifasciata. Frequent with the type at Alexandra Dock. L. puteolus, Turton. Very rare, and of small size. A few examples at Larne, Newtownards, and Downpatrick. Stewart recorded it from the Magheramorne bed.