some specimens the dorsal and ventral surfaces show a central area, depressed and wrinkled transversely to the length. Two genital papilla with pores, anterior to the anal aperture.

Abdomen.-Aborted, or perhaps represented by two fusiform appendages attached to the extremity of the thorax, between and in front of the junction of the ovisacs. Between their bases is the anal aper

ture.

Ovisacs.-Yellowish. Blunt at ends. Eggs arranged in multiserial order of 3 to 4 in breadth, and presenting hexagonal outlines.

DESCRIPTION OF MALE.

Length.-3.5 mm., usually attached to the back or side of the

female.

Head. Similar in shape to that of the female, but with antennules and antennæ proportionally longer, and projecting erect from base. The siphon is directed downwards, and not forwards as in the female, and just above it, below the cephalic shield, is a single eye slightly projecting in profile. The mandibles and maxillæ similar to those of the female.

Maxillipeds.-Not very disproportionate to each other in size. The inner pair similar to those of the female, but larger. The outer pair slightly exceeding the inner in length, two jointed, with the basal joint large, and the second joint short, broad, flat, and cheliform, something like the beak of a parrot.

Intermaxilliped processes are seen projecting like a pair of transparent lobes with a granular centre between the two pair of maxillipeds. Those of a young specimen I examined were proportionally much longer than those of adult specimens, suggesting that they may be survivals of ancestral appendages. These may possibly be what Van Beneden refers to1 when speaking of the maxillipeds of L. galei; he says, "On voit entre elles des pieces très distinctes du squelette cutanée."

Thorax.-Very small proportionally to the head, bluntly oval in shape, without traces of segmentation, except in immature specimens, which in both sexes are divided into five segments, which is also the case with L. galei and (Steenstrup and Lütken) L. elongata. The remarks of Van Beneden, in his recent Memoir on Brachiella Chavesii

1 "Recherches sur quelques Crustaces Inf.," Ann. des Sc. Nat. 1851.

upon the segmentation of Charopinus Dalmanni, figured by Kroyer, may be, perhaps, thus explained.1

Two genital styliform appendages project from the posterior ventral surface corresponding in situation to those of the female, slender in the middle, but broader at the distal end.

Between their bases are the orifices from which the spermatophores are extruded.

Abdomen.-Aborted as in the female. The two abdominal lobes are much stouter and broader, and of irregular ovoid shape. They bend backwards and upwards until they rest upon the dorsal surface of the thorax. In the immature stage they are almost globular, and project backwards from the point of attachment without any upward

curve.

1"Deux Lerneopodiens nouveaux." P. J. Van Beneden. De Belgique, No. 7, 1891.

Bull. Acad. Roy.

EXPLANATION OF PLATES.

FIG.

PLATE IX.

1. Lernæopoda bidiscalis, an immature male, showing segmented

thorax.

2. The same, ?, showing dorsal area flattened.

3. The same, showing ventral aspect.

4. The same, with a more oval thorax and larger outer maxillipeds.

5. An adult male.

6. Outer and inner maxillipeds of female with saucer-like tenaculum.

7. Do. do. another aspect.

8. Dorsal aspect of a female highly magnified.

9. Head of do. seen from above, showing antennules, antennæ,

and labrum.

10. Mandible.

11. Maxilla.

12. Siphon of female protruded from buccal aperture.

13. Mandible highly magnified.

PLATE X.

FIG.

1. Immature female of L. bidiscalis highly magnified.

2. Immature male do. do., showing intermaxilliped process.

3. Adult male do., s. spermatophore.

=

4. Do., ventral aspect, showing situation of intermaxilliped processes and spermatophores.

5. Extremity of outer maxilliped of male.

6. Discs and tenaculum of female.

7. Do., with unequally developed discs.

8. Intermaxilliped process.

9. Genital papillæ of female with pores. 10. Do. do. of male.

XVII.

REPORT ON THE ESTUARINE CLAYS OF THE NORTHEAST OF IRELAND. BY R. LLOYD PRAEGER, B.E., M.R.I.A.

[Read FEBRUARY 22, 1892.]

THE term estuarine clays, as used in the present report, is intended to signify those deposits, mostly of clay, which have accumulated in our existing bays and estuaries since the close of the Glacial period-a definition propounded by Mr. S. A. Stewart, of Belfast, who first pointed out the important evidence which these beds furnish as to the latest fluctuations of the sea-level on our shores. The estuarine clays have been described under the names of silt, drift, diluvium, alluvium, alluvion, and blue clay; the areas which they cover are commonly known as slob-lands, while the clay itself is locally called slob, sludge, or sleech. In their typical form, they consist of tough, homogeneous, unctuous blue clays, entirely free from admixture of gravel, sand, or pebbles, and containing a marine fauna rich in Mollusca, Entomostraca, and Foraminifera, which differs somewhat from that inhabiting the adjacent waters at the present day. The estuarine clays occupy large areas in and around many of the bays of the North-east of Ireland, and as they present beds of considerable thickness, which have been continuously laid down, and as their fauna lived on the spot where it is now entombed, they afford perhaps the best view of the geological history of the long interval that has elapsed since the close of the Great Ice Age-a more complete record, certainly, than the much studied contemporary raised beaches, which are too often but current-heaped remnants, with a miscellaneous fauna washed into them from the neighbouring waters. That the estuarine clays cannot be treated as mere recent deposits of mud, but are duly entitled to a place in the Post-tertiary series, is shown by the difference between their fauna and that of the adjoining waters, as well as by the fact that they are either contemporaneous with, or older than the aforementioned raised beaches, such as those at Larne, Kilroot, and Greenore, which have never been refused a place in the geological succession.

The typical succession of Post-tertiary beds in the North of Ireland estuaries, in ascending order, is as follows:

1. Boulder clay.

:

The Boulder clay, with its boreal fauna and scratched and polished pebbles, need only be mentioned here as the base on which the succeeding deposits are laid. Overlying it, in the Belfast estuary (which, on account of the extensive development of the beds there, and the excellent opportunities that have on various occasions been afforded for their inspection, may well be taken as a type), and elsewhere, is a fine, hard, red clay without pebbles, evidently produced by the washing down of the Boulder clay, and, with the next-mentioned bed, probably corresponding in age with the eskers. It is succeeded by fine red sands, generally unfossiliferous except for a few worn Foraminifera to attest their marine origin. These sands are extensively developed around Belfast; a full account of them and the associated strata, showing their distribution and characters, by James Mac Adam, F.G.S., will be found in the Journal of the Geological Society of Dublin, vol. IV., part ii., No. 2 (1850), to which the reader is referred.

The red sands are succeeded by a deposit of a widely different nature the submerged peat-a well-marked zone, which can be traced, usually underlying estuarine clay, not only around the Irish shores, but at many spots on the coasts of England and Scotland. At Alexandra Dock, Belfast, it was found twenty-seven feet below high-water mark; near Connswater, and at Tillysburn, Holywood, Ballyholme, Carrickfergus, Glenarm, Ballintoy, and Portrush, it may be, or has been seen between tides; at Downpatrick, in the estuary of the Quoile, it is again far below low water. It yields a flora of marsh plants-sedges, flags, and rushes; branches and fruit of hazel, alder, oak, willow, and Scotch fir, especially the first-named; elytra of beetles are frequent, and mammalian remains occur. It is the first bed showing the ushering in of the temperate conditions still existing, and may be considered the base of the estuarine clay series.

Resting on the peat, in the typical section which is being described, is the estuarine clay proper, which displays two zones, differing both