31. On the TRIASSIC STRATA which are EXPOSED in the CLIFF-SECTIONS near SIDMOUTH, and a NOTE on the OCCURRENCE of an OSSIFEROUS ZONE containing BONES of a LABYRINTHODON. By H. J. JOHNSTONLAVIS, Esq., F.G.S. (Read March 22, 1876.)

In describing the locality and geological position of the vertebrate fossils which were obtained from the Triassic rocks near Sidmouth, perhaps it would be as well to commence with a description of the coast-sections for a short distance east and west of that town.

Starting from the east, we find that the Marl* (which is the uppermost subdivision of the Trias of South Devon) makes its appearance at Branscomb Mouth, exposed beneath the Greensand and Chalk in the cliff-sections, and in the ramifying valley cut through by the small stream which runs out to sea at this point. It now forms the lower portion of the cliff under Littlecomb Hill and Branscomb Hill, being overlain by the Greensand and Chalk until it is exposed inland at Weston Mouth by the action of the little stream called Weston Water, which runs out here.

It again forms the base of the cliff under Dunscomb Hill, being still overlain by the Greensand and a small patch of Chalk; again it is exposed and partly excavated by the little brook at Salcomb Mouth; thence it forms the base of the cliff under Salcomb Hill, being now capped by the Greensand alone; it is then largely exposed on the surface in the valley of the river Sid.

A few yards east of where the Sid runs into the sea, the Upper Sandstone (of Mr. Ussher) crops out, forming a cliff overhanging the Sid, and constituting the bed of the stream for half a mile from its mouth, and also the whole valley except where covered by gravel, which Mr. Ussher tells me is in some places 15 feet thick, containing a bed of peat about a foot in thickness. The gravel is chiefly composed of chert, and contains teeth of Elephant, numerous specimens of which have been found by Mr. P. O. Hutchinson and others.

To the west of Sidmouth, at the end of the Parade, we meet with a low projecting cliff, called Chit Rock. Mr. Ussher, who has surveyed this district, tells me he has met with no evidence of a fault having existed in the valley; and therefore we may conclude that it is the continuation of the small exposure of sandstone which is seen to exist east of the river, as in section, fig. 1 (p. 276). At the western end of the Chit Rock we find a fault which has given the Chit Rock an upthrow of at least 40 feet; but it is very possible it may be as much as 80 feet, since it has no marl capping it, and in its lithological character resembles the middle of the Upper Sandstone. We see, on the western side of the fault, the Marl brought down within a short distance of the beach, there being a small mass of Sandstone exposed beneath it. All the Triassic beds from Branscomb up to the present place dip gently to the east; but now we find them dipping to the west; this only takes place for the distance of about half a mile; * See Ussher, Geological Magazine,' Decade II. vol. ii. No. 4, April 1875.

for the Sandstone which had disappeared, soon makes its appearance again, having formed a synclinal curve. During the whole of this distance it has been covered by the marl, which, as it advances westward becomes thicker, being less denuded; it has cappings of Greensand and chalk-gravel at Peake Hill and High Peake. The Sandstone continues to rise gradually to the westward; but the Marl and overlying Greensand have been cut down by atmospheric denudation, forming Windy Gap, which separates High Peake and Peake Hill-High Peake being the higher of the two, but resembling Peake in every other respect. The Sandstone gradually rises until, at a short distance to the west of High Peake, the Marl has been entirely denuded (save in a few places where through faulting it has been brought to a lower level) and it appears on the surface.

The upper marls are variegated, and especially in the higher part, east of Sidmouth, contain very thin layers of a greenish-grey sand mixed with a large quantity of mica, intercalated with layers of marl, varying in thickness up to two inches, but of the same light colour; they show ripple-marks, and occasionally contain pseudomorphs of rock-salt.

The marls between Weston and Branscomb Mouths contain a large quantity of gypsum, which at one time was worked at Branscomb Mouth. A few small veins are to be seen between Salcomb and Weston Mouths. The marls also contain bands of potato-stones enclosing a cavity lined with calcite. Mr. H. B. Woodward objects to my giving them the name of potato-stones, as they do not contain quartz crystals.

The Sandstone, especially at its upper part, where it resembles very much in lithological characters the upper beds of marl, contains a large number of pseudomorphs of rock salt, ripple-marks, and sun-cracks; but in no case have I met with rain-marks, which we might expect; neither have I met with any foot-prints. Some of the upper sandstones effervesce with hydrochloric acid. Between High Peake and Otterton Point the sandstones contain spherical masses sometimes almost like a cannon-ball, composed of iron pyrites; these are washed out of their matrix and lodge at the bottom of the little rocky pools.

The sandstones also contain curious irregular branching-shaped masses of a harder texture, which withstand the weathering and give the cliff a rugged aspect. It is worthy of notice that, at the points where the Marl reaches down to the beach, there are no reefs on the foreshore opposite, but a beautiful fine-grained red sand, except where large blocks of chert have fallen from the Greensand capping the cliffs; but wherever the Sandstone appears above the beach one sees large reefs running out to sea for nearly half a mile at low tide; it does not seem to be the sandstone itself which withstands the weathering, but these curious hard masses contained in it, since they occur in all the projecting points of the cliff formed by the sandstone strata.

Last autumn, while on a visit to Sidmouth for the second time, I had the good fortune to find the bones of a Labyrinthodont.

W.

Windy Gap.

2

These were brought to light at different periods during my month's stay. It may be mentioned that those described by Prof. Seeley are merely the bones which I considered capable of identification; for I met with a great number of small fragments dispersed throughout a particular series of beds situated about 10 feet from the top of the Sandstone. These bones were mostly found in fallen blocks which were derived from these beds in a little cove known as PicketRock Cove. It may be well termed an ossiferous zone, as it does not consist of one single bed, but of from one to four; not that I mean to imply that bones are only found in this zone, since Mr. Whitaker's Hyperodapedon was found at the very bottom of the Sandstone. This zone is characterized by lithological differences, inasmuch as the matrix is composed of much coarser sandstone, containing here and there masses of marl varying in size from that of a pea to that of a hen's egg. It is nearly hard enough in some places for buildingpurposes. In these beds ripple-marks are very plentiful. The fragments of bone which are found in this zone seem to be very slightly waterworn.

I cannot conclude without expressing my thanks to Messrs. H. B, Woodward, W. A. E. Ussher, and W. Whitaker for the kind assistance they have afforded me, and to Mr. P. O. Hutchinson, of Sidmouth, for the artistic diagrams with which he has furnished me.

P.S. Since writing the above I have received from the Rev. S. H. Cook some fragments of bone obtained by him about twenty years ago from the same zone west of Sidmouth, as well as one which he recently obtained from the small outcrop of sandstone with the ossiferous zone on the western side of the Chit-rock fault.

Below the ordinary red sand on the beach one finds a stratum of black sand which has been derived from the sandstone, but is of greater specific gravity than the red sand, which accounts for its position on the beach. Mr. R. W. Cheadle has kindly made a qualitative analysis for me, with the following rough results-Silica, magnetic iron oxide, manganese, titanium, and alumina.

[For the DISCUSSION on this paper see p. 283.]

32. On the POSTERIOR PORTION of a LOWER JAW of Labyrinthodon (L. Lavisi), from the TRIAS of SIDMOUTH. By HARRY GOVTER SEELEY, Esq., F.L.S., F.Z.S., F.G.S., Professor of Physical Geography in Bedford College, London. (Read March 22, 1876.)

[PLATE XIX.]

NOTWITHSTANDING all that has been done of late years by Prof. Huxley and those who have continued his labours, for the elucidation of the Labyrinthodontia, less is probably known of the structure and affinities of that group than of any other long-established Order of vertebrates. It may perhaps be an open question whether Labyrinthodonts can rightly be referred to an existing class of animals; for the nature of the affinities of these fossils with Amphibia, Palosauria, and Reptilia is a subject rather for inquiry than for dogmatism; and unfortunately the new materials now to be described are too few to do more than slightly modify accepted surmises.

No apology seems to be necessary for the restoration of Prof. Owen's name Labyrinthodon, because neither Prof. Huxley nor Mr. Miall have attempted to justify either its suppression or reconstruction, while I am inclined to urge that demonstration is wanting that any foreign Labyrinthodont genus, such as Mastodonsaurus, has ever occurred in the British Isles. The single dermal plate figured by Mr. Miall, so similar to one hereinafter described from Sidmouth, seems to me no evidence; for Labyrinthodonts like Crocodilia and Telcosauria may well have resembled each other in the dermal armour of allied genera; and in describing an English fossil closely allied to one of those originally described by Prof. Owen from Warwickshire, it seems better to refer it to the genus Labyrinthodon as constituted by Prof. Owen, there being no evidence adduced or available for the subdivision of that genus in the manner proposed by Mr. Miall.

To H. J. J. Lavis, Esq., F.G.S., we are indebted not only for the discovery of the present specimen, unexampled among Labyrinthodont remains for its beautiful preservation, but also for untiring labour and skill in extricating the fossil from the matrix, and reuniting its multitudinous fragments into the handsome and instructive remains of a right lower jaw exhibited.

The fossil is 13 inches long, and absolutely free from matrix, so that every aspect and its component structures can be studied. It demonstrates that the lower jaw does not consist of articular, angular, and dentary elements only, as generally described, from which it is evident that the jaw is not constructed according to the Batrachian type. In addition to those three bones, there are certainly separate splenial and surangular elements, and not improbably a separate coronoid bone also. These five or six bones in each ramus are arranged so as to enclose a deep narrow cavity at least 9 inches long, in the hinder part of the jaw, extending forward from beneath