102 Sizes, Agreeing in Nothing So Much As the Particularly Slender

102 THE GEOLOGIST. sizes, agreeing in nothing so much as the particularly slender and narrow shape of the leaflets and branches. They look like parsley leaves, coriander leaves, mimosa, and some again look like what they are — finely divided ferns. Figure 7* shows the peculiarly graceful character of the tribe. There are several other kinds of " opteris", with which, as the Scotch song says, "I'm laith to vex ye." But I must mention one that is not very common in the coal, but which has been found in a perfect state in some beds older than the coal, both in Ireland and in Scotland. This is the Adiantites Hibernicus, a fern first brought to notice by that eminent man and ardent naturalist, Edward Forbes. It is common in some rich fossil beds in the upper part of the Old Red Sandstone of Ireland. It puts one in mind of the fern which is the glory of Killarney—the King or Royal-fern, Osmunda regalis—about the same size, and with the spreading broad leaflets set on a broad stem. But whereas our Killarney friend carries her fruit on her head, that is to say, the terminal leaves and pinnee are changed into fruit-bearing spikes, the fern that grew in old old times on the margin of thePateozoic bogs has its lower or bottom pinnae crowded with seeds. (To be continued.) ON THE DISTRIBUTION OF CEPHALASPIS AND PTERASPIS IN ENGLAND. BY GEOEGE E. ROBERTS. I HOPE our scientific tourists of the approaching season will take their good eyes into Herefordshire quarries. For now that the Scotch mono poly of the Old Red fishes is broken up, they will be found to repay time and trouble, if searched for in that and the adjoining counties; and something like a reasonable history of these strange old littoral fishes may be the result of a single season's work. There is a great deal about them well worth, knowing, and their remains will be found tolerably abundant, though very fragmentary, both in the sandstones and corn stones ; and therefore I have a peculiar pleasure in intro ducing our primaeval fish-fauna to the notice of those on search already—or hoping to be as the season advances—for relics of ancient life. Before I call particular attention to some fruitful localities, let me say a few words upon the physical condition and geographical aspect of the age they lived in. Though I ought rather to say ages, for they anticipated the advent of the system they are popularly said to belong to—that vast life-era—the extent of whose inland-seas and shallow littoral ocean-zone we see in the sandy, shaly, and gravelly beds which contain our fishes, and of whose deep seas the thick-bedded * The figures of Sphenopteris ScMotheimii, Adiantites Hibernicus, and Osmunda regalis will be given in the next number. ROBERTS—DISTRIBUTION OF CEPHALASPIS AND PTEEASP1S. 103 limestones of Devon are witnesses—called by us Old Red or Devonian; and first appeared upon the stage in true Upper Silurian times ; for the Pteraspis Ludensis of the Lower Ludlow shales of Leintwardine (county Salop), is the oldest representative of the family. Its discovery in these older rocks, though of great interest, did not in the least surprise me; for a sea-deposit, so clearly marked out as littoral by its starfishes and its shrimp-like Crustacea, would be the natural home of shore-fishes, which Cephalaspides undoubtedly were. Moreover, the shells and fuci which the Lower Ludlow rock has everywhere in keeping, tell a certain tale of its shallow-water condi tion ; and enable us by studying them to read with greater ease and increased interest, the record written by succeeding seas. Indeed, if we are to understand the physical aspect of the Old Red age, we must make ourselves well acquainted with the foregoing Silurian; for no aid will be of greater value to us, or more beautiful as a study, than the slow and gradual transition from the deep-sea condition which prevailed over the border-counties I am calling attention to, during the accumulation of the marine limestone of the Wenlock series, and the inland lakes of brackish water, terminated, probably, by wholly freshwater conditions, which have left us the fine silty shales of the Upper Old Red as their legacies. And thus it comes to pass, that not only for the first stages of its new physical career, but also for the birth-place of its life-forms, the Upper Silurian age is insolubly linked with the Old Red Sand stone ; and in every exposure of these older rocks, which contain littoral crabs and star-fishes, we may reasonably expect to find the ancestry of the ancient shore-fishes I am describing. But though they thus anticipate the age they are popularly said to belong to, they did not—so far as we know—live beyond the close of the Old Red system; and beyond doubt their metropolis is in the grey and red cornstones of Herefordshire and Worcestershire. The position of these beds (see section, page 104), which are seen in many places in these border counties to pass through a tilestone series into the underlying Silurian, is now clearly made out, and only their fossil history waits our reading. And this must be learnt by us before the true contemporaneous relations of the two very distinct rock-series which we together know as the Devonian system can be cleared up ; before we can see what com munication, if any, existed between the shallow waters which laid sandy sediment in Herefordshire, and the deeper ocean, which has left us hard coral-rock and shells, in Devon. Upon the physical boun- . daries of these waters, Eichwald has some instructive remarks in a short memoir prefacing the fish-fauna of his " Lethcea Rossica," in which he points out the marked difference between fishes of the shore and fishes of the open sea, and describes some new forms of osseous fishes from the Devonian rocks of Russia, not unlike our English Cephalaspids. And now I will mention the results of my own hunting among the Old Red quarries, and I hope, by thus putting others upon the trail, many good fishes may be taken. For more specimens are wanted before even their (precise) position 104 THE GEOLOGIST. Great Conglomerate. /,/M ' Upper Sandstones. Upper Cornstones. m Cepkalaspis asterolepis and C. \ Lyellii, Pteraspig Lloydii (?), j Grits and Sandstones, ^ O c^vj // Lower Cornstones. Cepkalaspis Lyellii, Pteraspis') Grits. Lloydiiy and P. Lewisii. ) Upper Tilestones. Lower Tilestones. CephaZaspis Lyellii (?) and C.~\ ///•/ Mtvrchisoni, Pteraspis rostra- > A ///A Downton Sandstones. tits and P. Bamksii. ) I ^w' f Upper Ludlow Rocks. Pteraspis truneatus, P. Banksii,^ and P. rbstratus, Cepkalaspis > 1 Aymestry Limestone. Salweyii, C. Lyellii (?), Auch- > • enaspie Saltert. J Pteraspis Ludentia. Lower Ludlow Rocks, g, Pteraspis Ludensie. ROBERTS—DISTRIBUTION OF OEPHALASPIS AND PTERASPIS. 105 among fish-families can be decided. Probably a kinship existed between the two chief forms of ichthyic test of Oephalaspis and Pteraspis, and it is most likely that our noble friend, the sturgeon (Acipenser), will have to own them of his family; for, as Prof. Hux ley has lately pointed out, they bear, in shape and arrangement of head-plates, a great affinity to the genus Spatularia, a North American attache of our larger and caviare-giving fish. It may help the comprehension of those who are unfamiliar with the osseous head-shields of these old ganoid fishes, if I sketch the two forms whose acquaintance will be most easily made by exploring collectors, Oephalaspis and Pteraspis. Form of shell is a very deceptive guide both in fish and crustacean life ; indeed, if we made our affinities from this alone, one great genus would include many species of both orders, for the shape of Cephalaspidean bucklers is copied almost literally by several Crustacea. A new Harpes from the Silurian limestones of Oesel, figured by Eichwald, agrees not only in shape of head, but even a position of the eyes with Oephalaspis; while it would be a matter of serious concern where to draw the line between the head-plates of Eurypteris and Oephalaspis. But it is from the closest and most minute examination that species and even families are determined among those which lived during the infancy of vertebi ated life. A, Oephalaspis Head-shield. B, Pteraspis Head-shield (as usually found"). 1, Ornamented external layer. 1, External ridged layer. 2, Intermediate cancellated layer. 3, Internal shell layer. * A restoration of this is promised us by Prof. Huxley. Pteraspis Ludensis, the oldest fish with which we are at present acquainted, was found in the Lower Ludlow mudstones at Churchill Quarry, near Leintwardine, and has been well described and figured, side by side with its ally, Pteraspis truncatm, from the Upper Ludlow rocks, by Mr. Salter, in the "Annals of Nat. Hist." for July, 1859. VOL. IV. O 106 THE GEOLOGIST. P. Ludensis ranges up into the Upper Ludlow shales, in which it was found as far back as 1852 by Dr. Harley, of King's College. I have not heard of other Cephalaspids being found in Upper Ludlow rock, but in the Downton sandstone they reappear, and are abundant in the neutral ground lying between that rock and the tilestones, and still keep the company of Euryptera and Pterygoti. The Down- ton sandstone is well displayed near Kington; where in a quarry near Bradnor Hill, two forms of Pteraspis were discovered by Mr. Richard Banks. These are described and figured by him in the Greol. Soc. Journ., vol. xii., p.

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