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purpose here extends only to the description of certain forms found since the publication of the monograph referred to, and to the presentation of a few observations relative chiefly to distribution. And before proceeding to notice the various species seriatim, a few general remarks will not be out of place.

In considering the question of altitudinal distribution, it is quite possible that we might arrive at erroneous conclusions, owing to the mixing up of other accidental circumstances not connected solely with elevation. We find that Entomostraca are usually most abundant where there is a profusion of vegetation; in little sheltered bays, margined with sedge and rushes, and bearing luxuriant beds of Myriophyllum, Potamogeton, or other water-plants-lovely little inlets, which we may find plentifully on the shores of Windermere and Derwentwater. And when we notice that in elevated tarns the number, both of species and individuals, is comparatively small, it is well to remember that this may partly depend upon the fact that these sheets of water are mostly, owing to their exposure and want of shelter, almost entirely destitute of vegetation, except of a very stunted kind; so that the poverty of the fauna is doubtless dependent partly on these causes, and only indirectly through them on elevation and temperature. For it is not unusual to find in pools close to the margin of some lake a Crustacean fauna totally different from that inhabiting the lake itself. Thus, in some pools on the shores of Ennerdale Water, which had formed, apparently, in the hollows left by turf-cutters, and were filled with Myriophyllum, Utricularia, and Potamogetons, I took an astonishing number of various Daphnia, Lyncei, etc.-seventeen species in all; while along the whole length of Ennerdale Lake itself I could not succeed in capturing a single specimen of any kind. But the margins of this lake are excessively barren and stony; so much so, that in walking along its northern shore I could not detect a single patch of weed, and the net, when put into the clear water, collected nothing but little masses of spawn-of what animal I do not know. Still, I have no doubt that a prolonged search might have revealed spots more favourable to microscopic life, and that, even where no vegetation existed, Entomostraca might perhaps have been found-if not then, under other conditions of water or atmosphere. For vegetation does not appear to be absolutely essential to the lower forms of animal life. I have taken various Entomostraca in water where no vegetation, at any rate, higher than Diatoms or Desmids, existed; but in such situations they are always scanty, if existent at all, and the number of species capable of living under such conditions seems to be very limited.

In Ennerdale Water, however, this paucity of animal life would appear to be distinctly the result of lack of vegetation: it cannot be dependent on elevation, for the level of the lake is only 369 feet above the sea, and, as has been noticed, the pools close to it swarmed with life. It may be noted also that the members of the family Daphniadae scarcely ever occur, except where there is abundance of vegetation, while the Lynceida seem to thrive well on a stunted cover of Lobelia Dortmanna or Isoetes lacustris.

It may be interesting here to place side by side (as types of the very wide difference existing between the Crustacean faunas of weedy pools of low elevation, and exposed mountain tarns of great elevation) lists of the Entomostraca obtained in two such localities.

POOLS IN ENNERDALE: height above the sea, 370 feet.Daphnia reticulata, D. pulex, D. mucronata, Acantholeberis curvirostris, Ilyocryptus sordidus, Sida crystallina, Bosmina longispina, Lynceus harpa, L. quadrangularis, L. elongatus, L. truncatus, L. globosus, L. barbatus, Eurycercus lamellatus, Diaptomus castor, Cypris lævis, C. ovum.

ANGLE TARN, under Bowfell: height, 1553 feet.-Bosmina longispina, Lynceus elongatus, L. guttatus, L. exiguus, L. testudinarius, L. sphæricus.

DAPHNIA JARDINII, Baird (Figs. 9, 10).—This curious species has, I believe, not been previously figured; and, indeed, I am not aware that it has been noticed by any observer, except Dr. Baird (Edinburgh, New Philosophical Journal, vol. vi., 1857, p. 24). I took three or four specimens in Rydal Water in 1861, and from one of these the drawing given in the accompanying plate was made. Its claim to specific rank may, however, be reasonably doubted. The produced vertex, by which it is chiefly distinguished from Daphnia pulex, is known in the case of D. mucronata to be a variable character, and the form known as D. cornuta is acknowledged to be merely a variety of the latter species. D. Jardinii is indeed smaller and more slenderly formed than is usually the case with D. pulex, but I am not able to discover from my specimens any specific character more valid than that already referred to, nor does Dr. Baird's description indicate any such. On the other hand, it should be stated that the three specimens preserved in my collection all have the cephalic cornua, though of variable size and shape, and I do not remember that any specimens of the normal D. pulex occurred in company with them. The length of my largest specimen is one-sixteenth of an inch, exclusive of the posterior spine.

Daphnia pulex (Lin.) and D. vetula (Müll.) occur commonly in lowland pools; and in the peaty hollows in Ennerdale,

already referred to, I found also D. mucronata and D. reticulata, the latter in very great abundance. But in pools of this kind occurring at a greater elevation, the Daphniæ seem to give place to another member of the same family-Acantholeberis curvirostris-which will presently be noticed.

SIDA CRYSTALLINA (Müll.) occurs plentifully amongst reeds and rushes round the margin of lakes, but does not, apparently, reach any great elevation.

ACANTHOLEBERIS CURVIROSTRIS (Müll.).—This species is not uncommon throughout the British islands in pools of peaty water, ranging from near the sea-level to considerable elevations. It does not so often occur in clear lakes and tarns. Sprinkling Tarn, and Crag Lake, Northumberland, are the only such localities in which I have any record of its occur

rence.

ILYOCRYPTUS SORDIDUS (Liévin).-A rare and curious species, of which I found two specimens in my gathering from the peaty pools in Ennerdale. It had previously been found, though very sparingly, in two situations in Northumberland. and Durham.

DREPANOTHRIX HAMATA, G. O. Sars, is of not unfrequent occurrence in the upland districts of the north of England and south of Scotland, frequenting lakes and clear water. In the Lake district, I have found it in Rydal Water, Blea Tarn (Langdale), Little Langdale Tarn, and Easdale Tarn.

POLYPHEMUS PEDICULUS, Müll., though common in the moorland lochs of Northumberland and southern Scotland, is not so in the Cumberland district, the only lake in which I have found it being Derwentwater.

BOSMINA LONGIROSTRIS (Müll.) and B. LONGISPINA, Leydig, occur, one or both of them, in almost all pieces of water in the Lake district. The males of these animals differ remarkably from the females in having the anterior antennæ connected with the body by a sort of ball-and-socket joint, and in the tapered form of the abdomen. This sex is, however, rarely met with; the only place in which I have found it being a small rushy tarn on some hills, called the Humbles, on the north-western border of Northumberland. This pool contained abundance of the Bosmina, but scarcely any other species; and I found this to be the case also in a somewhat similar situation on the northern slope of Mickle Fell, in Yorkshire; but in this latter case my gathering contained no males.

LYNCEUS HARPE (Baird), a very common species in almost all clear pieces of water throughout the kingdom, and on the continent of Europe, seems little affected by elevation, being met with in almost all the pools, lakes, and tarns of the Lake

district.

LYNCEUS MACROURUS, Müll., is much rarer than the preceding species, to which it bears a striking general resemblance. Buttermere, Derwentwater, and Blea Tarn (Langdale) are the only localities in the Lake district where I have met with it. It seems to be a lowland rather than an alpine species.

LYNCEUS QUADRANGULARIS, Müll., is still more decidedly of lowland proclivities, being quite one of the rarer species in mountainous districts, but almost the commonest of British Lyncei in the plains. I have taken it, however, sparingly in Grasmere, Easdale Tarn, Derwentwater, Blea Tarn (Langdale), and in pools in Ennerdale. Its place in the waters of the lowlands seems in mountain regions to be usurped by the following species:

LYNCEUS ELONGATUS (G. O. Sars)—Fig. 8—which may be looked upon as the form most characteristic of mountain lakes, its strongholds being bleak, elevated sheets of water, such as Stickle, Angle, and Sprinkling Tarns, while at low elevations, and especially in small pools, it is much scarcer. In the lowland and southern districts of England it is not at all met with. When living in high, bleak tarns, it is often of a very deep, opaque brown colour, verging on blackness, and sometimes appears to be almost the only animal inhabitant of the water; but in lower and more sheltered situations it to a great extent loses its deep colouring. A very remarkable peculiarity of L. elongatus is that the carapace, though normally consisting of two valves, like all the rest of the genus, is very often found to be made up of two or three pairs of valves superimposed one on another. This condition is seen in the specimen represented at Fig. 8 of our plate, the six layers of carapace being plainly indicated by the minute tooth at the lower posterior angle of each. In this condition the edges of the several valves occupy very various positions. Sometimes all three (and I have never seen more than three) are pretty close together, as in the figure; at other times the edge of the uppermost comes nearly in the middle of the animal. It is remarkable, too, that the several coats do not separate in the process of exuviation, for the sloughs, which are often taken in great numbers along with the living animals, constantly show the several valves in union just as when alive. I cannot yet say whether the young are born in the multivalvular state, or whether it is a result of growth, but in every copious gathering of L. elongatus many specimens in this condition are sure to occur, and in some they form almost the greater part of the whole. This is the more interesting when considered in relation to a very curious species of the same family, Monospilus tenuirostris, one striking character of which consists in a somewhat similar but much more pronounced multi

plication of valves; and the question suggests itself—do we, in the case of I. elongatus, see a species which is undergoing a gradual transformation in the same direction?

L. elongatus occurs in all the gatherings which I have made in the Lake district, and is frequent also in similar situations throughout the north of England and Scotland.

LYNCEUS COSTATUS (G. O. Sars), seems to be a tolerably common inhabitant of lakes and clear water in moderate altitudes, but is seldom found in more elevated and exposed situations. Buttermere and Derwentwater are the only two localities in our Lake district where I have met with it.

LYNCEUS GUTATTUS (G. O. Sars).- Well marked forms of this species are undoubtedly very distinct from the foregoing, but I am disposed to doubt whether the differences ought not to be regarded as varietal rather than specific. It is not uncommon in similar situations, ascending, however, to greater altitudes, and ranging from the sea-level to a height of 1553 feet (Angle Tarn). The following are the lakes in which I have met with it: Buttermere, Thirlmere, Easdale, Langdale, Angle and Sty Head Tarns.

LYNCEUS TESTUDINARIUS, Fischer, is a widely distributed and very well marked species, and appears to haunt indifferently water of all degrees of exposure and elevation. It occurs in my gatherings from Buttermere, Langdale, Angle and Sty Head Tarns, and from pools on Eskhause, at an elevation of about 2000 feet.

LYNCEUS EXIGUUS (Lilljeborg).—A very small, but well marked species, occurring in almost all the waters of the lake districts, but more commonly in those of considerable altitude. I find it in Buttermere, Thirlmere, Derwentwater, Easdale, Langdale, Sprinkling, Sty Head, Stickle, Angle and Floutern Tarns, and in the river Brathay, below Skelwith Bridge.

LYNCEUS TRUNCATUS, Müller, is a common species in the low country, and at moderate degrees of elevation in the lake district, but is not so frequent in the higher mountain tarns, the greatest height at which I have found it being 915 feet (Easdale Tarn). It occurs also in Windermere, Grasmere, Rydalwater, Derwentwater, Langdale, and Blea Tarns; in pools in Ennerdale, and in the River Brathay.

LYNCEUS UNCINATUS (Baird).-This species is at once known by the upturned extremity of the rostrum and strongly toothed infero-posteal angle. Buttermere is the only one of the lakes in which I have found it.

LYNCEUS NANUS (Baird), the smallest of the British Lyncei, occurs at all altitudes. I have noticed it in Buttermere, in Floutern, Blea, Sprinkling, and Sty Head Tarns, and in pools on Eskhause and Honister Pass.

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