3000 feet in vertical thickness, it is possible that some of the the millstone grit, the whole representing a group of strata some

varieties

may have been evolved from earlier types, during the very long period of the accumulation of these strata. Although Spirifera trigonalis, with its var., S. bisulcata, are not known from any strata earlier than the Carboniferous period, yet it probably existed over some tract of the sea-bottom during pre-Carboniferous times.

I have already stated that in the Old Red Sandstone period, and in that of the calciferous sandstone series of the west of Scotland, we have no evidence from the contained fossils that the sea occupied the tracts where these strata were being deposited; but after the outpouring of the volcanic rocks forming our trappean hills, there appears to have been some change in the physical features of the country, the sea having apparently had ready access over the area as often as the land was depressed under its level. Mr Robert Craig of Beith, in his interesting paper "On the first appearance of certain fossils in the Carboniferous strata. around Beith and Dalry,"* points out that, in the strata overlying the lowest of the volcanic series of that district, and which belong to the calciferous sandstone period, there is a bed of coal representing an old land surface, and that over it, in a bed of argillaceous shale, the first of the group of marine organisms make their appearance. These appear in such force, and are represented by so many genera and species, as to lead me to believe that they must have migrated from some other tract of the sea bottom outside the area of the west of Scotland, where they had been flourishing, either in pre-Carboniferous times, or in the period represented by the fresh-water strata of the calciferous sandstone group. In this bed, Mr Craig has noted sixty species of molluscs, besides corals and crinoids; while amongst the Brachiopoda Spirifera trigonalis, and some of its varieties, make their first appearance. I have found the shell, on nearly equally low horizons of strata, in other portions of the coal-field around Glasgow, and it has also been obtained from strata of the same age in other districts of Scotland, as well as in England, Ireland, and other European countries where marine Carboniferous strata prevail.

What was the ancestor, in pre-Carboniferous periods, of Spirifera trigonalis and its varieties we do not know. Mr Davidson, the * Trans. Geol. Soc., Glas., Vol. v., p. 36.

eminent palaeontologist, states that the variety, S. bisulcata, has been by some assimilated with the Devonian S. aperturata, to which it approaches somewhat closely in form. I think that not only this species, but many others, may have been derived from Devonian forms by descent. Thus, amongst others, our abundant Spirifera Urii is believed to be identical with the Devonian S. unguiculus, and it has also been shown that it survived along with some other Carboniferous species until Permian times, in which formation it is known as Spirifera Clannyanus. In the lower limestone shales of the Beith district, Spirifera trigonalis on its first appearance presents us, as will be seen by the specimens exhibited, with at least three or four well-marked varieties, one of which has the mesial fold more produced than any yet described. This variety I have found in the upper cement limestone at Arden, near Thornliebank. One of the other varieties approaches closely to Spirifera acuta, which has not yet been identified from Scotland; the others agree with the typical varieties, S. trigonalis and S. bisulcata, although some of the latter are more transverse than are usually found. In the shales at Newfield, High Blantyre, a variety of S. trigonalis is found, which, in the extension of its hinge-area and elongated mesial fold, almost rivals that of S. triangularis, from which species it is known by its more numerous ribs. This wide variety is there the only form of the species that has yet been found. I also exhibit specimens of the ordinary varieties of S. trigonalis and S. bisulcata, from both the lower and upper limestone series of the west of Scotland; the species, as I formerly stated, ranging upwards into the millstone grit, being found in the sandstone and shales of that group to the north-east of Glasgow.

One of the largest and finest varieties of Spirifera bisulcata obtained in the west of Scotland, is that found in the shales overlying the cement limestone at Orchard, near Giffnock, on the Busby railway. The strata belong to the upper limestone series, and this form, so far as yet known, seems to be peculiar to that horizon. It is very deep between the valves, and comes very near to Spirifera mosquensis, a species not hitherto recognised from Scotland, being only distinguished from it by its fewer ribs. It is very probable that all these varieties of Spirifera trigonalis are only varieties produced by descent from one original type, which seems to have been very variable, the variations probably being

caused by the conditions of the sea bottom on which it lived. Mr Davidson states, that at the time when he commenced his investigations amongst the British Carboniferous Spirifera, there were about one hundred and seventeen described species. After a long and searching investigation, he came to the conclusion that eighty-six of these so-called species were mere synonyms and varieties, and out of the thirty-one species admitted to his lists, only some twenty-three have been satisfactorily determined. All this variation, therefore, favours the view that many of the closelyallied forms once ranked as species, are only varieties of one original type.

One point in connection with the distribution of Spirifera trigonalis and its varieties in our strata I wish to refer to before I have done, and that is its disappearance throughout a considerable thickness of strata, represented by the fresh-water beds of our middle coals and ironstones of the Possil and Govan group. The absence of decidedly marine remains from this group of strata, points to physical conditions that once more shut out the sea from the space occupied by their area, and during which the strata accumulated were such as had either grown upon land, or had been deposited in lake bottoms of fresh water origin. With the return of the sea, during the upper limestone period, returned also Spirifera trigonalis, and some of its varieties, as well as many other of the older forms of Carboniferous marine life. These maintained for a period a sort of shifting existence, until they finally disappeared, by the shutting out of the sea during nearly the whole time of the deposition of the upper Carboniferous coal measures. Evidences of these physical changes are derived from the study of the groups of fossils found in the various strata, these affording the only true key to the history and conditions of the fossiliferous sedimentary deposits of every geological period.

II.-On some Plants rare in the West of Scotland, observed during last Summer. By Mr JAMES RAMSAY, Vice-President. Mr Ramsay stated that on 3d July, 1875, along with Prof. A. Dickson, he had visited the island of Cumbrae, and while passing along the margin of a field of oats, just coming into ear, they discovered among the corn a great many plants of the Nightflowering Catch-fly (Silene noctiflora), an annual species, confined in Scotland entirely to the eastern counties. This was the only

time he had ever seen the plant growing, and he had no doubt it had been introduced with seed corn, and would likely establish itself in Cumbrae, for in a neighbouring field they found the Penny cress (Thlaspi arvensis), also a denizen of the east, but which is seldom seen in the west, excepting occasionally on ballast or rubbish heaps.

On the 10th of the month they visited Benlomond, but neither in ascending nor descending the mountain was anything met with that they had not seen there before. One of the party, however, who in coming down had taken a different route from the others, succeeded in picking up specimens of three plants worthy of notice. The Holly fern (Polystichum lonchitis), is chiefly found on the highest mountains of Scotland and Wales. It was last summer reported as having been got on Benvoirlich, but it has not hitherto been recorded as found on Benlomond. The next to be noticed, Potentilla alpestris, is a very attractive species, with deep rich, golden yellow flowers, and the only stations given for it in the "British Flora" are the Clova and Breadalbane mountains. The third noticeable species was Arenaria verna, which is quite common in the east, growing plentifully on Arthur's Seat and the Corstorphine hills, but not recorded hitherto as found in the west. It is noticeable that neither of these plants, nor Sibbaldia procumbens, which grows abundantly on the mountain, are mentioned in Hennedy's "Clydesdale Flora," although Benlomond comes within the range of its stations.

JANUARY 25TH, 1876.

Professor John Young, M.D., F.R.S.E., President, in the chair. Messrs Alexander Hill, Daniel Wilson, George Rennie, and William Baxter, were elected ordinary members of the Society.

SPECIMENS EXHIBITED.

Mr Francis G. Binnie exhibited two specimens of Trichoptera, united by authors under the' Halesus digitatus of Schrank, and remarked that three species are confused under this name, two of which-viz., those exhibited-seem to be British. The first, H. radiatus, Curt., is not uncommon by the Clyde at Carmyle, and by the Allander, also in the vicinity of the Cloch. The second,

H. digitatus, Schr., is a larger insect, more yellow in colour, and has the longitudinal grey streaks in the apical cells of anterior wings more or less broken up, giving a freckled appearance to that portion of the wings. The inferior abdominal appendices of the male are widely furcate; these parts in H. radiatus being simple, with the apex excised. It occurs along with the last, by the Clyde and the Allander. Both species are mixed under digitatus in Stephen's collection. For the nomenclature I am indebted to Mr R. McLachlan, the first living authority on the group, who is at present engaged upon a monographic revision of the European Trichoptera.

Mr John A. Harvie-Brown, M.B.O.U., corresponding member, exhibited a fine specimen of the Great Grey Shrike, Lanius excubitor, which had been killed at Tongue, Sutherlandshire, on 7th Dec., 1875, and was sent to him in the flesh by Mr John Crawford. Mr Peter Cameron exhibited specimens of Macrophya albipunctata, Fallén, from Perthshire and Aberdeenshire. It is a species new to the British fauna, and has been recorded hitherto only from Scandinavia, but he had also specimens of it from eastern Germany, where it is in all probability confounded with M. albicincta.

Dr Dewar exhibited a pair of live Wild Cats, Felis catus, Linn., which had been obligingly lent by Mr Henry Martin, Buchanan Street, and remarked that this species was frequently met with in Inverness-shire. He said he knew of one gamekeeper who had obtained a dozen specimens in a short time. He had no doubt that the pair exhibited were the real Wild Cat, and not merely specimens of the Domestic Cat run wild.

Mr Harvie-Brown corroborated Dr Dewar's remarks. He had seen Wild Cats among the birch woods of Sutherlandshire, where they are not uncommon, and considered that the markings of the fur and the conformation of the head and tail were sufficient to distinguish them from the domestic animal.

PAPERS READ.

I-Note regarding the occurrence of the American Bittern, Botaurus lentiginosus, in Islay. By Mr JAMES LUMSDEN, F.Z.S.

At the November meeting of the Society Mr Lumsden placed upon the table a Bittern, which had been killed in Islay in the previous month. At that time he could not confidently state to which species the bird belonged, not having had an opportunity