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not to the juncture of two vertebræ, nor to the extremity of the body, but to the middle of the centrum.'

VERTEBRÆ OF MOSASAURUS, from the chalk near Lewes.— (M. Stenodon.)-Wall-case A-B.-On the recess above the specimens of Geosaurus, is a small block of chalk, to which are attached two caudal vertebræ, possessing the characters above described, and by which I was enabled to identify them with the corresponding bones of the celebrated Maestricht reptile, of which I had then read, but never, in my most sanguine moments, had indulged the hope of finding any vestiges in my native hills. A posterior dorsal vertebra from the same locality is placed near them; I have subsequently obtained a caudal vertebra imbedded in flint (from near Brighton); a few other portions of the vertebral column have, I believe, been collected from the Sussex chalk since my removal from Sussex. The remarkable character above pointed out, of the coalescence of the chevron-bone with the body of the vertebra, is well shown in these two caudals from Lewes. M. Cuvier observes, that there is no known reptile in which this bone is soldered to, ("soudé”), and makes a part of, the centrum; it is a character peculiar to fishes, and must have greatly augmented the solidity of the tail.

No teeth similar to those in the jaws of the Mosasaurus have been obtained from the English chalk; but some large smooth conical teeth of an acrodont reptile, symmetrically elliptical like the pterygoidal teeth of Mosasaurus, were found in the same stratum as the vertebræ, and are probably referable to the same species. In 1831, a portion of the lower jaw with teeth of a similar character, was found in the chalk near Norwich, and of which I received drawings from the late Mr. Samuel Woodward. Other specimens of equilateral

1 "Elles forment une grande partie de la queue, et les faces de leur corps sont en ellipses, d'abord transverses, et ensuite de plus en plus comprimées par les côtes. L'os en chevron n'y est plus articulé, mais soudé, et fait corps avec elles."-Ossemens Foss. loc. cit. p. 327.

2 In "The Fossils of the South Downs; or, Illustrations of the Geology of Sussex," 1822, there are figures and descriptions of these specimens, pp. 242-246; tab. xxxiii. and xli. I would especially direct the observer's attention to the deep incision observable on the posterior vertebra in this specimen, which must have been made before the bones were imbedded in the chalk.

teeth anchylosed to the alveolar ridge of the mandibular bone, have been discovered; and assuming the probability that these jaws, teeth and vertebræ, of the Mosasaurian type belonged to the same genus, but differed specifically from the Maestricht animal, Mr. Charlesworth proposed to distinguish it provisionally by the name of Mosasaurus stenodon.

To resume. The jaw of the Maestricht animal is three feet nine inches in length; the entire length of the skeleton is estimated at twenty-four feet; thus the head is nearly onesixth of the total length-a proportion according with that of the crocodiles, but differing from the monitors. The tail is only ten feet long, and therefore but half that of the total length; while in the crocodile the tail exceeds the entire length of the body by one-seventh; its shortness is owing to the abbreviation of the bodies of the vertebræ.

This animal formed an intermediate link between the tribe of saurians without pterygoidal teeth, the monitors,—and those with them, the iguanas: its only approach to the crocodiles was in a few partial characters, and in those general bonds of connexion which re-unite the entire family of oviparous quadrupeds. The bones of the extremities are but imperfectly known; those attributed to the Mosasaurus are said to indicate members adapted for natation rather than for progression on land, and to support the inference of M. Cuvier, that the original was a marine animal of great strength and activity, having a large vertically expanded tail, capable of being moved laterally with such force as to constitute a powerful instrument of progression, capable of stemming the most agitated waters.1

Teeth in every respect analogous to those of the Maestricht reptile were discovered by Dr. Harlan of Philadelphia, from the equivalent deposits of the cretaceous formation, the

In the Memoir of M. Adrien Camper, "Sur quelques parties moins connues du squelette des Sauriens Fossiles de Maestricht," there are figures of several metacarpal or metatarsal bones from Maestricht, which the author describes as resembling those of the Crocodile, and probably belonging to the great saurian; among them is a small conical shaped bone, termed an ungual phalanx, but which has more the character of a dermal tubercle or spine; the figure, however, is too small and indefinite to show the true nature of the original.

In

ferruginous sands of New Jersey, in the United States. 1830, my lamented friend, the late Dr. Morton of Philadelphia, (whose early death is so much to be deplored,) sent me specimens and casts of teeth of Mosasaurus, which agreed in every respect with those from the Netherlands; teeth of this kind are figured in Dr. Morton's "Synopsis of the Organic Remains of the United States :" Philadelphia, 1834. Of late years, vertebræ and other bones of the same genus have been found in these deposits; some of which, collected by Prof. Rogers, are figured and described in the Quarterly Journal of the Geological Society of London.

POLYPTYCHODON. -Wall-case B.—In a frame on the top of this Case there is a group of bones, some of which are nearly entire, others mere fragments, imbedded in plaster, and belonging to a large marine reptile; they are from the greensand strata near Hythe in Kent, and were collected and presented to the Museum by H. B. Mackeson, Esq. No part of the cranium or jaws has been discovered; but in the same deposits, as well as in the white chalk, very large conical longitudinally ridged teeth frequently occur; these have received the name of Polyptychodon. Prof. Owen, assuming that the teeth he has thus designated belong to the same species of reptile as the bones found in the same strata, has described the above isolated parts of the skeleton under the

same name.

These consist of fragments of bones referred to the coracoid, ilium, ischium, and pubis ; and portions of the humerus, part of a femur, tibia, and fibula, and several metatarsal bones. Of these, the thigh-bone, of which above two feet of the shaft remains, at once separates the reptile to which it belonged, from the Iguanodon and other gigantic saurians whose relics are occasionally found in the same formation, for it has no medullary cavity, its centre being occupied by a coarse cancellated structure, as in the cetaceans; this fragment is fifteen inches in circumference. The metatarsal bones are the most perfect of these remains; the longest was two feet in length, and four inches in transverse diameter in the middle.

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Neither teeth nor vertebræ have been found, and the visional name "Polyptychodon" simply indicates that the

large, conical, ridged teeth, and these detached bones, may probably appertain to the same genus or species of aquatic saurians.

In a subsequent section we shall enter upon the most interesting department of our present subject,--the history of those gigantic terrestrial saurians whose remains have been chiefly obtained from the strata of the south-east of England, and of which this division of the Gallery contains an interesting series.

[graphic]

LIGN. 45.-IGUANODON QUARRY, NEAR CUCKFIELD, SUSSEX. 1820.

1. Blue clay, forming the floor of the quarry.

2. Tilgate grit.

3. Soft sandstone.

4. Drift, or diluvium.

3

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