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Pleurotomaria subcancellata. (PL XVIII. fig. 6.)
Shell large, conical, formed of six rather quadrate volutions, somewhat depressed at the upper part and convex below; volutions ornamented by numerous concentric striae, decussated by the still finer lines of growth, forming a series of quadrangular meshes, and producing a neat and uniform reticulation; umbilicus large; mouth transverse.
This fine and large Pleurotomaria, measuring 2£ inches across the base, is nearly equal in size to the P. delphinuloides Goldf., figured in the Geol. Trans. vol. vi. t. 33. f. 4. It very closely resembles the perfect specimens of P. reticulata, from the Kimmeridge clay of Wootton Basset (England), both as regards the squarish form of the volutions and the general markings; from that species it rather differs in size, and in the somewhat depressed and central position of the mesial band.
Locality. —Illawara (New South Wales).
I have observed in a fragment of the rock from the deposit at Illawara, a well-defined impression of another species of Pleurotomaria, nearly related to P. conica Phillips, in having a bicarinated mesial band, and numerous small, oblique, rather acute striae on each volution; it differs however from that species in being smaller, more elongated, and acutely conical.
Discoid, convex, with a minute umbilicus; aperture lunate, short, depressed by the preceding whorl; lip thickened, with a deep sinus in the front.
This shell has very much the aspeot of a Goniatite, but I have not been able to detect septa in any of the specimens hitherto examined. The lines of growth form very fine slightly elevated ridges on the surface, curving backwards from the minute umbilicus. It somewhat resembles B. stamineus Conrad, but the aperture is rather less expanded.
Locality Illawara (New South Wales).
Theca. (J. de C.Sowerby.)
General form elongate, pyramidal, obscurely threesided, straight, one side generally flattened; external surface either smooth or transversely or longitudinally striated.
This genus has been instituted (in MS.) by Mr. James Sowerby, for the reception of certain forms having considerable resemblance to the genus Creseis among the Pteropoda, and probably belonging to the same family.
The Orthoceras trianrjidare Portlock, t. 28 A. fig. 3., as well as the form represented in t. 29. f. G, 7., may belong to this genus, and other species are found in the silurian strata.
Theca lanceolata. (PI. XVIII. fig. 8.)
Shell elongate, gradually tapering; section obtusely trigonal, surface marked with numerous transverse striae, which become arched as they pass over the posterior (?) portion of the shell.
In the cast of the flattened sides of the shell, a somewhat obtuse ridge may be observed, not visible on the exterior surface. Length, 2 inches; diameter at top, nearly half an inch.
This species offers, by its form, a passage into the Conularice, and is near to C. elongata Portlock. Locality Illawara (New South Wales).
Conularia levigata. (PI. XVIII. fig. 9. a. b.)
Shell smooth, elongate, pyramidal, rectangular, gradually decreasing, two of the faces larger than the other two; faces slightly concave, longitudinally sulcated at the lateral angles, ornamented with equal transverse ridges, forming a slightly obtuse angle in the mesial furrow, where they alternate with each other; ridges terminating at the bottom of the lateral channels, curving slightly upwards, and alternating with each other, producing a somewhat granulated ridge.
In the species of Conularia from the carboniferous and silurian strata of England, the section of the pyramid is quadrangular, which form is also observed in those from the Devonian strata of the Rhenish provinces. M. Roemer has figured another species, C. acuta, in which the sides are unequal, producing a lozenge-shaped section; and subsequently M. De Koninck has described one, C. irregularis, from the carboniferous limestone of Belgium, of a similar figure. The above-described species from Australia is therefore interesting; for although two of the sides are larger than the adjacent ones, the section is rectangular, and not rhomboidal. This species differs from the C. irregularis, not only in the form of the section, but in the transverse ridges alternating in the centre of the faces, and not being continuous over them, as represented by De Koninck in that species.
The number of transverse ridges within a certain space (half an inch), differs from those Conularia? previously described. If the figures carefully represent these markings, in C. ornata there are 12; C. Gervillei, 20; C. Brongniartii, 13; C. irregularis, 15; in a specimen of C quadrisulcata, from Coalbrook Dale, 25; one from near Glasgow, 20; in our species, C. levigata, 16. The ridges and intervening spaces are apparently smooth.
Locality. — Illawara and Raymond Terrace (New South Wales).
Shell elongate, conical, gradually tapering; section somewhat oval; septa numerous, concave, slightly undulated; siphuncle circular, large, nearly marginal.
The imperfect state of preservation of the specimen prevents the defining of any good specific character. In general form it approaches the 0. undulatum Sow.; the shell very gradually increases in size, the septa being about a quarter of an inch apart. Diameter of largest portion, 2 inches.
Locality. — Yass Plains, New South Wales.
Bairdia affinis. (PL XVIII. fig. 10.)
Shell obtusely fusiform, tapering at both ends.
This species appears to be intermediate between the Bairdia curtus and B. gracilis (M'Coy); it is, however, not so fusiform as the former, and the posterior end not turncate, as in the latter species. In the same stratum are also found numerous specimens of a species of Cythere, too much compressed for correct determination.
Locality. — A dark bituminous limestone, from Booral.
Of this family have been observed some specimens of an Icthyodorulite, very much resembling the one figured in Mr. Prestwich's Memoir on the Geology of Coalbrook Dale; they are found at Booral, with the minute crustaceans above noticed, and Littorina jUosa.
General Observations.—In the notice of the ancient flora of the Australian continent, an allusion was made to the absence of certain characteristic forms generally found in the carboniferous system of northern Europe. In directing the attention to the fossil contents of the series of strata immediately underlying these plant-bearing deposits, a stiking general resemblance is at once perceptible to many forms occurring in some divisions of the Palaeozoic system of the northern region. Viewed as a whole, that is, including the Palaeozoic series of New South Wales and Van Diemen's Land, a great variation appears to have taken place in the mechanical and chemical conditions of the deposits in different localities, apparently producing a modifying influence on the distribution of the organised beings. Mr. Darwin, in speaking of Van Diemen's Land, remarks, —" The strata containing these remains are singular, from the extreme variability of their mineralogical composition. Every intermediate form is present, between flinty slate, clay slate passing into greywacke, pure limestone, sandstone, and porcelanic rock; and some of the beds can only be described as composed of siliceo-calcareo clay slate." Some portions of the limestone from Mount Wellington cannot be distinguished from the ordinary Derbyshire mountain limestone.
Although the species constituting the Palaeozoic fauna of Australia, &c, are not very numerous, it may