Mr. Fierke states, are scattered about the district, but are usually unproductive.

Pond at Tothby, Lincolnshire, dug in 1871.-Particulars communicated by Mr. J. E. Mason and Mr. J. B. Davy. Of special interest from the fact that the date of excavation is known. Situate on the clay near the foot of the Wold, in the corner of an arable field (T. C. Johnson's) at Tothby, on the borders of the parishes of Alford and Rigsby, and said to be quite isolated from other water. Two small fence-ditches, sometimes containing a little water received from the under-drains, open upon the pond; but Mr. Mason, in whose knowledge of the locality I have the utmost confidence, expresses the opinion that it is in the highest degree improbable, next to impossible, that a flood should have caused a communication with any other pond or water-course. Of the plants, none are of kinds likely to have been intentionally introduced; duckweed and two Potamogetons are conspicuous. Both the common newts occur, and water-bugs and beetles abound, but Mr. Mason has not seen a fish of any kind, although the nearest ponds are well stocked with sticklebacks. Of molluscs, Mr. Davy, in 1891, obtained two species, Limnoa peregra and Sphærium lacustre, both in fair plenty. The presence of the former, which, it is said, is generally the first to appear in newly-formed ponds,' is of no special interest, but the establishment of a bivalve-shell

1 See G. Roberts, "Topography and Nat. Hist. of Lofthouse," 1882, p. 167.

(S. lacustre) in an isolated pond dug only twenty years before is certainly worthy of note.

Pond at Rigsby, Lincolnshire.-Mr. Mason and Mr. Davy have also favoured me with particulars of another pond, probably much older than the last, and remarkable for possessing a surprisingly rich molluscan fauna. Situate in the parish of Rigsby (in the “nineteen acres," abutting in part on Rigsby Wood), of small size, surrounded by arable land, and apparently perfectly isolated. The nearest ditch, it is true, is within about eleven yards, but the water in the pond is considerably above the level of that in the ditch, and Mr. Mason assures me that no possible flood can have reached the pond; with the exception of the water carried in through the pipe-tiles of a small under-drain, it gets every drop from rain and surface drainage. It is apparently very old, and was probably dug at a time when the surrounding district was an unenclosed sheepwalk, in which case, of course, it is just possible that sheep or cattle may have been instrumental in introducing shells or ova adhering to their feet or legs.' There are no plants likely to have been intentionally introduced, duckweed (Lemna minor), a Potamogeton, some grasses, &c., making up the principal vegetation. Mr. Davy and Mr. E. Woodthorpe, who have searched for shells, have discovered no less than four species of bivalves and five univalves, representing together five

'The same may be said of most ponds which appear to be more ancient than the surrounding enclosures, as well as of those situate on large unenclosed pastures.

genera: Sphærium corneum, Sphærium lacustre, Pisidium fontinale, Pisidium pusillum var. obtusalis, Planorbis nitidus, Planorbis nautileus, Limnoa peregra, Limnoa stagnalis, and Ancylus lacustris.

Ponds at Finchley, Middlesex.-Near the middle of a meadow at Finchley (by the side of the foot-path to Hendon, and in the third field from the road at Eastend, Finchley)' are two ponds, without inlet or outlet, which lie near together upon a ridge slightly higher than the surrounding ground, perfectly isolated from other water, and which, it seems certain, can never have been affected by floods; they are evidently artificial, but probably very old, and neither is of large size, the larger measuring about 29 × 10 yards, and the smaller about 14 X 7 yards. In the case of ponds near large towns or cities having many shell collectors one can never be absolutely certain that molluscs have not been introduced intentionally or unintentionally by human agency, but it is unlikely that this often happens, and I know of no reasonable ground for such a suspicion in the present case. Ivy-leaved duckweed (Lemna trisulca), water-thyme (Elodea canadensis), frog-bit (Hydrocharis morsus-rana), and a Potamogeton are the principal water-weeds, and there are none of kinds likely to have been planted by man. Molluscs occur in abundance, the bivalve Sphærium corneum being plentiful in the mud, and very fine. In the larger pond four species, belonging to four genera, are found, all in good numbers:

1 This field, I find, is already being cut up for building purposes.

Sphærium corneum, Planorbis carinatus, Limnæa stagnalis, and Ancylus lacustris; while the smaller one, about thirteen yards distant, contains Sphærium corneum, Planorbis carinatus, Limnæa stagnalis, and Limnæa truncatula; and some idea of their individual abundance may be gathered from the following note of four caddis-cases-selected from a number collected in both ponds-bearing, together, no less than forty-five shells. (1) Five shells attached, two of Sphærium, one of Limnæa, and two of Ancylus; (2) ten shells attached, eight of Sphærium, one of Planorbis, and one of Limnæa; (3) fourteen shells attached, eleven of Sphærium, one of Planorbis, and two of Limnæa; (4) sixteen shells attached, one of Sphærium, and fifteen of Planorbis.

Pond near the Black Hills, Leeds.-During a period extending over some twenty-four years Mr. W. Nelson has obtained Sphærium lacustre, Pisidium pusillum, Planorbis nautileus, Planorbis vortex, Planorbis carinatus, Planorbis corneus, Planorbis contortus, Physa fontinalis, Limnæa peregra, Limnæa stagnalis, and Ancylus lacustris from this pond, which is of small size, isolated, as Mr. Taylor assures me, from other water, and with no inlet except "a natural drainage from the field." In times of heavy rain there is an overflow of surplus water, but this disappears in or spreads over the land

1 Mr. J. W. Taylor, of Leeds, has obligingly looked over the shells from these ponds and those at Welton-le-Wold, Tothby, and Rigsby, determining the Pisidia, and confirming my naming of the other kinds.

and has never been seen to reach a small stream which runs along at the bottom of the field, perhaps 150 yards away. The shell-fauna, it will be seen, is a wonderfully rich one, comprising, as it does, eleven species belonging to six genera, including two bivalves and no less than five kinds of coil-shells or Planorbes. But the pond is additionally interesting from the fact that a number of species seem to have been introduced quite recently. During 1860-3, when Mr. Nelson was in the habit of collecting there, it yielded only four species, Sphærium lacustre, Pisidium pusillum, Planorbis nautileus, and Limnæa peregra, so that since that period its fauna seems to have received a surprising number of additions. About 1873, Mr. Nelson resumed his visits to the locality and found Planorbis corneus, but no further kinds were obtained till 1883, when during frequent visits, he found six others, Physa fontinalis and Planorbis vortex in the spring, Planorbis carinatus, Limnæa stagnalis, and Ancylus lacustris a little later, and finally, in June, this small, but prolific pond yielded its fifth Planorbis, Pl. contortus. Mr. Nelson, who has published these facts,' is a collector of very great experience and a naturalist of ability, so that I dare not suggest that all the shells ultimately found probably existed in the pond, overlooked, during 1860-3, and Mr. Taylor and Mr. J. Beevers, who collected with him, agree that the four species named were the only forms in the pond at that time. The case is at least

1 W. Nelson, "Journ. of Conch.," iv. (1883), 117.