probable that it has often been "top dressed," a process which would quickly add to the depth of the soil. It should, however, be mentioned, that some years since, a field, in the north part of the county Tipperary, was broken up, that had a soil fourteen inches deep, and this field a man, seventy years old, knew to be exactly 110 years in grass. As the average depth of soil, in this part of that county, is from ten to twelve inches in depth, it would leave about 2.5 inches of soil to grow in the century, which is very similar to the results found near Caerleon.

V.-NOTE ON THE CAUSE AND NATURE OF THE ENLARGEMENT ON SOME CRINOIDAL COLUMNS.

A

By JOHN ROFE, F.G.S.

MONG a great number of specimens of Crinoidea from the Mountain Limestone collected by me during several years past, there are many parts of columns which shew an enlargement of the diameter or bulging similar to that described by Miller as representing "the remedial effect of calcareous secretion in repairing an injury of the joints of the stem," and some few portions have occurred having the appearance of a small column rising from the centre of a larger one as shewn in Woodcut fig. 1.

These last, for some time, were a puzzle not only to myself but to several friends better able to give an opinion on the subject. The small column a seems to be growing from the centre of the larger one without any appearance of a head or of side arms, and without any apparent cause; but further examination of a large number of specimens, an accidental fracture of one of them, and the subsequent dissection of others, suggest an elucidation of this difficulty, and of the cause and nature of these enlargements generally, and at the same time give a clue to the process of the growth of these Zoophytes.

The column of a Crinoid appears to have been not unfrequently used as a place of attachment for Corals, Bryozoa, or Serpulæ. Phillips (Geol. of Yorks., vol. ii, pl. 1, fig. 61) figures the Calamopora parasitica on a stem, and MM. Edwards and Haime (Monographs Pal. Soc.) giving it M'Coy's designation Favosites, also figure and describe it as usually adhering to the stem of an Encrinite. Another Coral, with which this note is more particularly connected, is described by McCoy as Jania crassa, and subsequently as Cladochonus crassus, and he states that "the mode of attachment of the young is most usually by the early branches growing in a circle round a Crinoidal stem." It is over and around the coral thus attached to the Crinoidal column that the enlargement above alluded to is very frequently formed. The coral having fixed itself to and surrounded the column prevents its further natural growth laterally; but the zoophyte when enlarging its column, which it evidently effected by secreting and depositing fresh shelly matter on the outside, encloses the body or cup of the coral with the column, and by so much increases the size. Certainly in most cases, and probably in all, the

divisions of the ossicula of the column are carried round the intruder, and shew on the outside as at b, fig. 1.

The specimen fig. 1 is evidently a section of one of these enlarge

ments broken across, from which the coral has been removed, probably at the time of fracture. In my collection there is nearly half the circle of a Jania which has thus been removed from a column to which it does not shew any appearance of having been attached further than by close contact. Fig. 1 c.c. indicate moulds left in the enlarged column from the coral having been removed.

Fig. 2 is a small fragment of a column with the Jania surrounding it, but not enclosed with shelly matter. Specimens in this state are very rare, and probably may be accounted for by the death of the Crinoid occurring before the enlargement of the column was made. a.a. shew the calices of the coral.

Fig. 3 is from a section cut across an enlargement of the column where the coral is surrounded by the Crinoidal matter. It may be here seen, as above stated, that the coral has attached itself to the column, and by gemmation eventually surrounded it; after which the Zoophyte, whilst increasing the size of its column, has enclosed the coral by a sort of exogenous secretion of shelly matter, as indicated in the section at b.b.; a.a. being the calices of the coral which apparently were left open whilst the coral lived, but in some specimens they are entirely closed in. This specimen also illustrates what is above stated in respect to fig. 1, for it will at once be observed, that if the coral is removed there would remain the small central column in the middle of the larger one, as in that figure.

In the specimen fig. 3, one of the Corallites is well preserved, and shews a structure which fully justifies the doubt of MM. Edwards and Haime as to the affinities of this Coral (Brit. Fossil Corals, p. 164). Fig. 4 is a magnified section of one of the calices, and fig. 4a. is a more highly magnified view of part of the same. It appears to be a tabulated coral, and, so far as I know, not yet fully described. I am indebted to Mr. Henry Woodward for calling my attention to the structure of the coral, as I should probably have overlookod its peculiarity, not being myself so familiar with this family as with the Crinoidea.

VI. NOTES ON THE GEOLOGY OF LUDLOW.

By ROBERT LIGHTBODY, F.G.S.

HAVE long thought that the vallies of the Onny and the Teme, both above and below Ludlow, had once formed an estuary, and that the promontory on which the town stands had been thrown up by some convulsion blocking up the valley, and turning the part above the town into a lake, which (by faults or otherwise) eventually caused an opening for the Teme between the Castle and Whitcliffe. Lately, in making a drain on the N.E. side of Castle-street, a quantity of rather coarse, and very well rounded gravel was exposed in sitú, and below it was a bed of fine brown argillaceous sand. The pebbles were Silurian, chiefly Lower Ludlow. One which looks like Wenlock, contained Stromatopora concentrica; another mass was composed entirely of Rhynchonella navicula, from the band at the top of the Aymestry Limestone.

This appears to confirm most appositely my original opinion, as the gravel is very similar to that found in the bed of the valley, both above and below the town, and appears to have been elevated with the site of the town. It could hardly have been deposited since the elevation. The line of fault, which appears to have accompanied the upthrow, runs east and west (about 100 yards north of this gravel), and I believe is crossed by another fault, running between the Castle and Whitcliffe, and giving passage to the Teme.

About half a mile east, at the Gravel Hill, and at 40 feet higher, there is a fine bed of gravel, but of a very different kind, consisting principally of the debris of the Old Red, chiefly Cornstone, and which makes binding and solid-surfaced gravel walks, in consequence of the clay mixed with it, whereas the lower level gravel, as well as the small outlier, which I first mentioned, is perfectly loose, and consists principally of Silurian and Cambrian pebbles, washed down from the upper Onny valley and mixed with sand, which sometimes

occurs in thin beds.

In the first instance, when was this Upper Gravel deposited? It must have been formed at the time of the denudation of the thick series of Old Red Beds, that once filled up the interval between the Titterstone, and Brown Clee Hills; the Clee Hills themselves being preserved by the capping of Basalt spread over them.

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Secondly, at what level? Was it originally washed into the bottom of the valley, and then elevated to its present position (as I have assumed the deposit of gravel in the town was), or was it formed at some very remote period, when its site was part of the lowest ground in its neighbourhood, and received the debris of the Cornstone beds above it? Or is it not probable that both these causes influenced its position? Its site being on the platform that extends Eastward from Ludlow, towards the Titterstone Hills, seems to favour the elevatory theory.

However, a very long period must have elapsed since the deposit of this gravel, as not only is the valley cut down to the depth of probably 100 feet, but is covered by a thick bed of rounded gravel composed almost entirely, as before mentioned, of the debris of the Cambrian and Silurian rocks. There appears to be no trace left of the Cornstone gravel, which seems all swept away, except the one outlier noticed here. I do not know of any other gravel of the same Cornstone quality in this neighbourhood. The thick bed of Silurian and Cambrian gravel is found South of Ludlow, on both banks of the Teme, and is excavated largely for ballast; Mammoth teeth have been found in it both at Wooferton S., and at Middleton, N.E. of Ludlow.

There would appear to have been at least three periods of elevation-First, when volcanic action heaved up the two Clee Hills, elevating at the same time the whole Old Red and Carboniferous strata, and no doubt cracking and faulting them in various directions. Thus the action of the sea and rain was enabled to wear down all the beds, except where they were protected by the sheets of Basalt covering the summits of the Clee Hills.

There was probably another series of gradual upheavals, on one or both sides of the Teme valley, which enabled the river to cut down its bed much deeper relatively to the high level gravel, and which was consequently left nearly 100 feet above the present level of the valley.

At that time probably, what is now the course of the Teme and its affluents, was a strait or estuary open to the sea (just as the vale of the Severn is supposed to have been), but it is now occupied by a thick bed of gravel composed of the debris of the rocks of the Longmynd Stiperstones, and other hills of Cambrian and Silurian age. This gravel is loose, and intercalated with thin beds of red sand, which increase in thickness near Church Stretton (as seen in a ballast pit near the Railway), as if they had originated from a wash of the Permian beds near Shrewsbury, through the narrow strait at Stretton.

The third upthrow has, I conceive, given rise to the ridge on which the town and castle of Ludlow stand, carrying up with it a portion of the gravel that once covered the bottom of the valley, and damming the water above it, until the river eventually found its way through the cracks produced by the upheaval, and thus formed its present course.

In favour of this view, there is an undoubted fault running across

the top of Corve-street eastwards, under the north side of the Churchyard and Castle, and thence straight up towards the gorge of the Teme at Downton Castle, leaving a depressed angle of Old Red on the north, as far as Downton Bridge, and heaving up the Ludlow beds on the south. This fault is not laid down in the Survey Map; but in the days when this district was surveyed there was less attention paid to this subject than at present, and I hope (if my view be correct) that in a future edition it may be inserted. This main fault (which is accompanied by several minor ones-also not laid downand which probably aided in directing the course of the river) runs in a line radiating from the Titterstone and slightly diverging from the principal fault which is laid down in the district map as running through Leinthall Earls and Moor Park, to the Titterstone Hills, throwing up the Ludlow and Aymestry beds at Tinker's Hill and Caynham Camp, in the midst of the Old Red to the southeast of its course.

VII.-NOTE ON A NEW TRILOPHODONT CRAG MASTODON.

THE

By E. RAY LANKESTER, B.A. Oxon.

THE collection of Mr. Baker, at Woodbridge, contains a tooth from the Suffolk Bone-bed, indicating a Mastodon of the section Trilophodon. The tooth appears to be the upper penultimate molar of the left side. Its chief peculiarities are its great breadth, approaching M. (Trilophodon) tapiroides; the shortness of the ridges, the cingulum well marked in parts; the absence of a posterior and presence of an anterior talon. It apparently belongs to Falconer's section, "Colliculi obtusi-valliculæque transversæ.' From a number of measurements and examinations of specimens of M. angustidens in the British Museum, of M. Borsoni and tapiroides in Paris (which I have to thank M. Lartet for very kindly showing to me), and M. Borsoni at Le Puy in the Haute Loire, I consider that this tooth comes nearest to the corresponding tooth of the huge Pliocene Mastodon Borsoni, though the cingulum and talon (very variable parts of the tooth) are unusually marked in Mr. Baker's specimen.

Not the least interesting part of the specimen under notice is the presence of a matrix occupying the valleys of the tooth, undeniably identical with the sandstone nodules which I have described as containing a fauna differing from that of the Red and Coralline Crags, and approaching the Belgian Diestien beds, containing Pyrula, Conus,' a small species of Cassidaria hitherto mistaken for Nassa conglobata and Isocardia in comparative abundance. This Mastodon tooth is the first specimen of terrestrial mammalian remains I have seen invested with the sandstone matrix. It furnishes the direct evidence which was wanting to prove that the terrestrial fauna of the Suffolk Bone-bed, like the Cetacea and sharks, was earlier in date not only than the Red and Coralline Crags, but than the sandy deposit which embedded it and the breaking up of which furnished the

1 The Conus is given on the authority of Mr. Searles Wood.