Among conifers of the Pine and Araucarian type we mark the first appearance in this system, in at least Scotland, of the genus Thuja. One of the Helmsdale plants of this genus closely resembles the common Arbor Vitæ (Thuja occidentalis) of our gardens and shrubberies. It exhibits the same numerous slim, thick-clustered branchlets, covered over by the same minute, sessile, scale-like leaves; and so entirely reminds one of the recent Thuja, that it seems difficult to conceive of it as the member of a flora so ancient as that of the Oolite. But not a few of the Oolitic plants in Scotland bear this modern aspect. The great development of its Cycadaceæ,—an order unknown in our Coal Measures,—also forms a prominent feature of the Oolitic flora. One of the first known genera of this curious order,—the genus Pterophyllum,—appears in the Trias. It distinctively marks the commencement of the Secondary flora, and intimates that the once great Palæozoic flora, after gradually waning throughout the Permian ages, and becoming extinct at their close, had been succeeded by a vegetation altogether new. At least one of the Helmsdale forms of this family is identical with a Yorkshire species already named and figured,—Zamia pectinata: a well marked Zamia which occurs in the Lias of Eathie appears to be new. Its pinnate leaves were furnished with a strong woody midrib, so well preserved in the rock, that it yields its internal structure to the microscope. The ribbon-like pinnæ or leaflets were rectilinear, retaining their full breadth until they united to the stem at right angles, but set somewhat awry; and, like several of the recent Zamiæ, they were striped longitudinally with cord-like lines. ([Fig. 133.]) Even the mode of decay of this Zamia, as shown by the abrupt termination of its leaflets, exactly resembled that of its existing congeners. ([Fig. 134.]) The withered points of the pinnæ of recent Zamiæ drop off as if clipped across with a pair of scissors; and in fossil fronds of this Zamia of the Lias we find exactly the same clipped-like appearance. ([Fig. 135.]) Another Scotch Zamia ([Fig. 136]), which occurs in the Lower Oolite of Helmsdale, resembles the Eathie one in the breadth of its leaflets, but they are not wholly so rectilinear, diminishing slightly towards their base of attachment; they are ranged, too, along the stem or midrib, not at a right angle, but at an acute one; the line of attachment is not set awry, but on the general plane of the leaf; and the midrib itself is considerably less massive and round. A third species from the same locality bears a general resemblance to the latter; but the leaflets are narrower at the base, and, as the print indicates ([Fig. 136]), so differently attached to the stem, that from the pressure in the rock most of them have become detached; while yet a fourth species ([Fig. 137]), very closely resembles a Zamia of the Scarborough Oolite,—Z. lanceolata. The leaflets, however, contract much more suddenly from their greatest breadth than those of lanceolata, into a pseudo-footstalk; and the contraction takes place not almost equally on both sides, as in that species, but almost exclusively on the upper side. And so, provisionally at least, this Helmsdale Zamia may be regarded as specifically new.
CONE.