the latter having been procured by Mr. Keeping for the Cambridge Museum.

In the cuttings of the Louth and Lincoln Railway we get again the succession of some of the beds. The actual junction with the Neocomian I did not see, as it was covered by drift. In the next cutting to the west we have the following section ::-

Thin limestone band, 4 in.

Blue shale, 9 ft.

Hard band of hydraulic limestone, 8 in., with Ammonites pectinatus (Ph.), Lucina minuscula, Ostrea gibbosa, and Discina latissima.

Light blue dicey clay, with shale full of Lucina minuscula.

The same papery shales with numerous fossils (Amm. biplex, Cardium striatulum, &c.) occur in the next two cuttings; and probably intermediate to them are the soft blue, not very fossiliferous, clays of a brick-yard by the railway-side, with Amm. biplex, Lucina minuscula, and Ostrea gibbosa; in this case, where we have the most complete section, we are struck with the general resemblance of the series to that at Kimmeridge; and this is the more noticeable, because the next good exposure, that at Nettleton Hill, shows us clays above the paper-shales, which are less and, indeed, scarcely fossiliferous, perhaps 30 ft. in thickness. The paper-shales here, i. e. at Acre House, are very fossiliferous, and yield Discina latissima, Belemnoteuthis, Ammonites pectinatus, Avicula vellicata, and Homomya gracilis (?). The series here, however, though possibly complete, cannot be so thick as in the south, as the Lower Kimmeridge is met with at the base of the hill at Holton-Moor station, and the dip is certainly not great.

I have not traced these beds further north; but Mr. Judd records their recurrence, after having been covered by the Chalk, in Filey Bay, where they contain the same fossils, together with Lingula ovalis in abundance, which, in spite of Dr. Waagen's quoting it as characteristic, I have everywhere else found to be a rare fossil in the Upper Kimmeridge, and to characterize rather the lower portions.

Everywhere then, as already remarked by Mr. Judd, the uppermost portion is thinly stratified and slaty. The contained suite of fossils have quite a facies of their own. We remark the commonness of Aptychi and Teuthiform Cephalopods. Discina latissima seems absolutely characteristic, although Prof. Phillips records a fossil by that name from the Oxford Clay. Astarte lineata, and Avicula vellicata, though rarer, also seem peculiar. Lucina minuscula is the bivalve that seems hitherto to have escaped description, and which crowds every surface; and though it is also met with far more rarely in the lower beds, by its abundance here it becomes really characteristic. The Cardium striatulum is the C. lotharingicum of Waagen's list, and, though more abundant in the upper beds, is scarcely characteristic, unless indeed we ought to divide the species. The remaining fossils are either rare or are also met with in lower beds; but their number is few. Of the whole list of Mollusca, containing 21 certain species, 14 are peculiar, and 7 are common to lower or higher beds-one, Ammonites pectinatus (Ph.), occurring also in the

Portland rock. The number of those that pass upwards is no doubt really greater where the two sets of beds are fully developed.

It thus appears that the upper portion of the Kimmeridge Clay can be satisfactorily marked off by lithological and paleontological characters into one connected series, and has therefore good claim for recognition. The sequel will show how far it is distinct from the beds below.

LOWER KIMMERIDGE.

The lower series consists of thick beds of clay, offering little lithological distinction, except in the neighbourhood of the Coral Rag; and if they are divided at all, it must be palæontologically. Dr. Waagen does this, including in the Lower Kimmeridge some feet of the clays at the base, and calling the rest Middle Kimmeridge; and Mr. Judd, in his paper on the Speeton Clay*, follows him for the strata of Filey Bay, and indicates the Lincolnshire pits which he considers to belong to either region.

The only positive indication of the nature of the Middle Kimmeridge, which Dr. Waagen states at 500 ft. thick, and which therefore ought to be the main mass and most often met with, is his list of 12 fossils, which, he says, are such as are commonly met with on the Continent in the zone of Pterocera Oceani. Of these, however, 4 (viz. Amm. mutabilis, Panopœa tellina, Opis suprajurensis, and Exogyra nana) he himself records from the lower beds also. Of the remainder, Amm. Berryeri and Lucina Elsgaudia (substriata) occur in the lowest beds at Weymouth; the Pholadomyo (2) are so badly preserved in the Kimmeridge Clay, as well as scarce, that it is impossible to place much reliance on them. Cardium pseudoaxinus is quoted by Thurmann from the lower zone also, and is certainly rare. Exogyra virgula occurs throughout.

There are left Rostellaria nodifera and mosensis, the latter of which is certainly most common in the upper portion; but they do not appear to be universally characteristic of the zone of Pterocera Oceani.

There is therefore nothing special about this collection of fossils which would justify the separation of the beds from those below; in fact, the different species are so united by occurring together in various localities, that two different faunas cannot be made out; and though minor zones may be recognized, as in the Upper Kimmeridge, they are often very local.

Judging, as we must do, for the general correlation of the beds, by the general assemblage of the fossils, it appears to me that the Middle Kimmeridge (that is, a series of beds containing a special Middle fauna, as exhibited elsewhere) is absent from England, although, the deposition of the beds having been continuous, some of them must be undoubtedly contemporaneous with the Middle period. The special fauna is that which abounds in Gasteropods of the genera Pterocera, Nerinaa, Natica, and Chemnitzia, together with many varieties of Panopoa and Pholadomya, and in some cases various * Quart. Journ. Geol. Soc. vol. xxiv. p. 240.

Echinoderms. Only the discovery of such a fauna would justify the recognition of Middle Kimmeridge beds.

All the rest, then, I include under the title Lower Kimmeridge, with the exception of a few beds forming the passage from the Coral Rag. Undoubtedly we might call the latter Lower Kimmeridge and all the rest Middle, as it would appear that Oppel would have done; but there are objections to this. In the first place, the thickness of these passage-beds is quite inconsiderable compared with the others; they are also only developed, as it would appear, where the Coral Rag is present, and contain in a large proportion a Coralline fauna; but, chiefly, the fossils of the clays above them do, and their fossils do not, bear comparison with those of the zone of Astarte supracorallina, as will be seen in the sequel.

The series may be best studied inland, particularly in Lincolnshire, which agrees with Dorsetshire in this as in the upper part.

The Horncastle pits, cited by Mr. Judd as belonging to the Middle Kimmeridge, are three in number. They expose some thickness (30 feet) of clay, with a few septarian stones, which, however, are not very fossiliferous. They probably belong to the uppermost region, as I could not find in them any examples of Amm. serratus. They contain, however, fossils associated with that Ammonite elsewhere; and its absence only marks a region in the series. The fossils here obtained are:

Ammonites mutabilis, Sow.
Rostellaria mosensis, Buv.
Dentalium Quenstedti, Bla.
Cerithium crebrum, Bla.
Cardium striatulum, Sow.
Lingula ovalis, Sow.

Avicula ædilignensis, Bla.

Pecten Grenieri, Cont.

Astarte supracorallina, D'Orb.

Nucula Menkii, Röm.
Nucula, sp.

Corbula Deshayesia, Buv.
Arca reticulata, Bla.
Anatina minuta, Bla.
Homomya compressa, Ag.
Thracia depressa, Sow.
Serpula intestinalis, Ph.

We see at once that this is a fauna quite distinct from that of the upper beds at Fulletby, two miles to the N.E., and that we have reached a region as distinct palæontologically as it is lithologically. As these pits, from their stratigraphical position, as well as their contained fossils, are certainly as high in the Lower Kimmeridge as any seen in Lincolnshire, it is important that we should examine this list, incomplete as it no doubt is, to see if it affords any justification for a separation between the beds here and the lower ones at Market Rasen and elsewhere. Now, of the seventeen here quoted, every one is found in company with Amm. serratus in other pits in Lincolnshire; and I fully believe a longer search would reveal that Ammonite here. Three also, namely Avicula ædilignensis, Thracia depressa, and Serpula intestinalis, go down to the very lowest beds. This set of pits, therefore, cannot be separated from the rest; are they all, then, to be called Lower, or Middle Kimmeridge?

Bearing in mind the different horizons of species, as before mentioned, in different localities, which will account for the presence of Rostellaria mosensis, although it is not a very common fossil here,

we find among the remainder, first, the very species that gives its name to the Astartian zone, Astarte supracorallina—and, again, Corbula Deshayesia and Nucula Menkii, the first of which is always, and the second usually, characteristic of lower beds; and these, with Cerithium crebrum, are the common fossils. The latter is a near ally, if not a variety, of Cerithium limaforme (Röm.), which is also characteristic of the lower beds. Thus, standing alone, these pits seem to me to present a fauna comparable to the Lower and not to the Middle Kimmeridge; and if they are not to be separated from the beds with Amm. serratus, the conclusion becomes more certain.

If these are Lower Kimmeridge, the rest, of course, are also, and we need only a description, and not so particular a discussion of their fossils.

The next exposures of this upper portion are at the south side of the Louth road at Market Rasen, and at Hamilton Hill, near that place. No clear section is here seen; but a rather peculiar fauna is found in the large septarian doggers scattered about, and which are generally formed round large Ammonites, such as Amm. Berryeri. Several series of such doggers, some more septarian than others, are found in the various clay-pits. The fossils here are:

Ammonites Berryeri, Les. biplex, Sow.

yo?, D'Orb.

Nucula obliquata, Bla.

Avicula nummulina, Bla.
Rhynchonella pinguis, Röm.
Astarte supracorallina, D' Orb.

In the cutting east of Brigg, at the most easterly portion, is seen dark clay, which contains similar fossils to those at Horncastle, viz. :

Rostellaria mosensis, Buv.

Cerithium forticostatum, Bla.

Anatina minuta, Bla.

Exogyra nana, Sow.

Lingula ovalis, Sow.

Arca reticulata, Bla.

Ostrea dilatata, Sow.
Discina elevata, Bla.

Serpula intestinalis (?), Ph.

In the Wrawby cutting the beds are now too rotten to give much chance of seeing fossils; in the most easterly portion, however, occurred Amm. biplex, Astarte supracorallina, Cerithium crebrum, Nucula Menki, Serpula tetragona, and Pentacrinus, sp.

The above exposures are in descending order; and we see in them the gradual introduction of species that occur more abundantly below, though the region of Amm. serratus is not yet reached; there is, however, nothing in them that would justify their separation from the beds below as Middle Kimmeridge.

Yet they have a facies in common that may serve to separate them as a subzone, namely the absence or rarity of Amm. serratus and the presence of abundance of Rostellaria mosensis and Anatina minuta. This latter character does not hold for the two pits mentioned near Market Rasen, whose peculiar fossils prevent their correlation; but they are probably the lowest of all these.

The beds above mentioned, in the Wrawby cutting, are succeeded by some thickness of very gypsiferous, but unfossiliferous, clays, the joints of which weather yellow. The occurrence of gypsum in the Kimmeridge clay is also mentioned by Prof. Phillips (Geology of