connected with this subject, we proceed to the examination of the specimen before us.

FOSSIL MARSUPIAL ANIMAL OF STONESFIELD.—(Phascolotherium.')—— Wall-case G.-The following is Mr. Broderip's account of the discovery of this fossil: "Some years have elapsed since an ancient stone-mason, living at Heddington, who used to collect for me, made his appearance at my rooms at Oxford, with two specimens of the lower jaws of mammiferous animals, imbedded in Stonesfield slate, fresh from the quarry. One of the jaws was purchased by my friend Professor Buckland, who exclaimed against my retaining both, and the other I lent him some time ago.” It is now

in the British Museum.

The discovery of the remains of undoubted mammalia in the lower oolite of Stonesfield, was first made known by Dr. Buckland in his Memoir on the Megalosaurus, in 1823, in the following words: "The other animals that are found at Stonesfield are not less extraordinary. Among the most remarkable are two portions of the jaw of the Didelphys, or Opossum, being of the size of a small Kangaroo Rat, and belonging to a family which now chiefly exists in America, South Asia, and New Holland. I refer the fossil in question to this family on the authority of M. Cuvier, who has examined it; and without the highest sanction I should have hesitated to announce such a fact, as it forms a case hitherto unique in the annals of Geology, viz. that of the remains of a land quadruped being found in a formation subjacent to the chalk." 3

In the course of the quarter of a century that has since elapsed, six specimens of one side of the lower jaw, belonging to three species of mammalia, have been obtained from Stonesfield; and what is most remarkable, no other recognisable parts of the skeleton have been discovered.

STRUCTURE AND AFFINITIES OF THE FOSSIL MAMMALIA.

Phascolotherium; signifying Ancient phascolomys, or pouch-animal; indicative of its affinity to the Wombat of New South Wales.

2 "Observations on the Jaw of a fossil Mammiferous Animal found in the Stonesfield Slate." By J. W. Broderip, Esq. See "Zoological Journal," 1828, p. 1.

"Geol. Trans." New Series, vol. i. p. 398.

These mammalian jaws belong to very small animals, and are referable to two genera. One of these, the Amphitherium, appears to have been an insectivorous mammal; it had thirtytwo teeth (twelve molars, one canine, three incisors) in the lower jaw; its marsupial affinities are doubtful.'

The other genus, Phascolotherium, presents in its dental and maxillary organs the true characters of the Marsupialia, Baron Cuvier pointed out the extent and position of the inward inflection of the angular process of the lower jaw observable in the fossil, as indicating its marsupial affinities; for in the placental mammalia the same degree of incurvation is not present. This fossil mammalian has four true molar teeth, three false molars, one canine, and four incisors (three only remain in the specimen), in each ramus of the lower jaw; thus agreeing with the living species of Didelphys.

LIGN. 80. RIGHT SIDE OF THE LOWER JAW OF A MARSUPIAL MAMMALIAN; FROM STONESFIELD.

The condyle of this jaw presents the same form and degree of convexity as in the genera Didelphys and Dasyurus; the general shape and proportions of the coracoid process resemble those in the zoophagous marsupials; but in the depth and form of the entering notch between this process and the condyle, it corresponds most closely with the Thylacinus, a solitary genus of Australia (the Hyena of the colonists),

1 66

Amphitherium Broderipii" of Professor Owen. See "British Fossil Mammals," pp. 29-70, for figures and an elaborate account of the Stonesfield Mammalia.

whose term of existence seems fast waning to its close.' Professor Owen concludes with the following remark:—“ Connecting the close resemblance which the molar teeth of the Phascolotherium bear to those of the Thylacine, with the similarities which have already been shown to exist in the several characteristic features of the ascending ramus of the jaw, I am of opinion that the marsupial extinct genus indicated by the Stonesfield fossil, was nearly allied to Thylacinus, and that its position in the marsupial series is between Thylacinus and Didelphys."

GEOLOGICAL INFERENCES. From what has been stated, it is evident that these mammalian remains from Stonesfield prove the existence at the commencement of the Oolitic period, of the two grand divisions of the class Mammalia, namely, the marsupial, and the placental. Commenting on this remarkable fact, Sir Charles Lyell observes, that "the singular accident of our having as yet found nothing but the half of the lower jaws of seven individuals, and no other bones of the skeleton, is alone sufficient to demonstrate the fragmentary manner in which the memorials of our ancient terrestrial fauna are handed down to us. We can scarcely avoid suspecting, that the two genera above described may have borne a like insignificant proportion to the entire assemblage of warm-blooded quadrupeds which flourished in the islands of the oolitic sea.' "93

3 "Manual of Elementary Geology," p. 270. This eminent philo. sopher, in his late Address on retiring from the chair of the Geological Society, again adverts to this important fact." Yet no small diligence has been used by collectors for more than a quarter of a century to obtain even the smallest isolated bones from these beds. I can only compare the capricious chance which has hitherto put us in exclusive possession of these seven mammalian jaws, with the equally strange accident recorded by Dr. Mantell in his career of discovery in the Wealden. He computed that in the course of 20 years he had found teeth and bones of the Iguanodon which must have belonged to no less than 70 distinct individuals, varying in age and magnitude from the reptile first burst from the egg, to one of which the femur measured 24 inches in circumference. Yet it was not until the relics of all these individuals were known, that a solitary example of part of a jaw-bone was obtained."-Address delivered at the Anniversary Meeting of the Geological Society of London, Feb. 21, 1851, by Sir Charles Lyell, F.R.S.

CHAPTER IV.

PART VI.

FOSSIL SHELLS AND CORALS.

TERTIARY AND OOLITIC GASTEROPODOUS SHELLS-UNIVALVES FROM MINCHINHAMPTONSHELLS IN SEPTARIUM-SHELLS FROM GRIGNON, HORDWELL, AND THE CRAG-CORALS AND OTHER ZOOPHYTES-NUMMULITES OF EGYPT.

FOSSIL SHELLS.-Table-cases 15 and 18.-The fossil shells deposited in these Table-cases are arranged zoologically; that is, as gasteropodous mollusca, without reference to their geological relations: thus the remains of extinct species and genera of molluscous animals that inhabited the seas of the oolitic period, and were contemporaries of the marine reptiles, the Ichthyosauri and Plesiosauri, which engaged our attention in the earlier pages of this chapter, are placed with the univalves that sported in the seas of the comparatively recent periods of the London Eocene, and the Crag.

The

The shells in Case 15, are chiefly from tertiary deposits; there is a fine suite from Hordwell,' and from Grignon. fossils from the Great Oolite of Minchinhampton are particularly deserving attention, not only on account of the recently discovered species from that formation, but also for their remarkably perfect state; for they have been extracted from the rock with great skill.

SEPTARIUM WITH SHELLS.-Table-case 15.-In this Case there is a group of shells which affords an instructive illustration of the different aspects in which the same species may occur in a fossil state. The specimens to which I allude are

See my "Geology of the Isle of Wight," p. 171.

on the right hand of the observer, and may readily be identified by the annexed Lign. 81.

The fossil, Lign. 81, fig. 2, is a polished slice of indurated argillaceous limestone, from the tertiary strata at

2. A polished slab of the Septarium.

3.-A cast of one of the shells, in calcareous spar.
(nat. size.)

Bracklesham Bay, Sussex, and is part of a septarium abounding in spiral univalves (Turritella). Fig. 1 represents a shell, extracted from soft clay; and fig. 3, a cast in calcareous spar, from the septarium. In the polished slab, fig. 2, sections of numerous shells are seen. The dark partitions, or septa, are veins of spar, which occupy interstices that