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derable expansion of the pulmonary cavities took place in these air-breathing marine lizards.

The bodies of the vertebræ are subcylindrical, and their articular surfaces nearly flat; there are two pits on the under part; the hæmapophyses and costal processes are not anchylosed to the body; and the hæmapophyses consist of two distinct lamine which do not coalesce distally into a spine, and form a true chevron-bone.1

The paddles are composed of fewer and more slender bones than in the Ichthyosaurus, and must have been of a more elegant form, and of greater flexibility. The carpus consists of a double row of round ossicles, which are succeeded by elongated metacarpals, and these by slender and slightlycurved phalangeal bones.

PLESIOSAURUS DOLICHODEIRUS.- -Wall-case D.-The specimen on the top of this Case is invested with a classical interest, for it was the subject of the admirable Memoir on this remarkable genus by the present Dean of Llandaff, (the Rev. W. D. Conybeare,) on the Plesiosaurus dolichodeirus (long-necked), read before the Geological Society, Feb. 20, 1824, and published in the "Geol. Trans." vol. i. New Series. In the Case below, there is another specimen of the same species from Lyme Regis ; it is nine feet in length, has the two right paddles, and exhibits the under surface of the lower jaw. A third specimen of this species, consisting of the trunk and paddles, is deposited in the upper compartment of Case F.

This species presents such extraordinary deviations from the ordinary saurian type, in the great length of its neck, and the extreme smallness of the head, that the correct interpretation of its characters and affinities, at the dawn of

1 For anatomical details consult "Brit. Assoc Report," 1839.

2 This specimen is figured in "Geol. Trans." vol. i. new series, Pl. XLVIII. p. 381. It was discovered and developed by the late Mary Anning, of Lyme Regis, and purchased by the late Duke of Buckingham for (I believe) 1057. I had the pleasure of being present when Mr. Conybeare read the Memoir at the meeting of the Geological Society in Bedford Street, Covent Garden; the specimen was placed in the narrow vestibule at the entrance, for want of room. Some years afterwards I saw it, in company with Dr. Buckland, at the princely mansion of the Duke of Buckingham, at Stowe. On the dispersion of the treasures of nature and art in that noble collection, it was bought for the British Museum.

British Paleontology, attests in a striking manner the sagacity, and consummate skill, and profound knowledge of the Cuvierian philosophy, of our eminent countryman, the Rev. W. D. Conybeare.

The

In the first specimen, the cranium and jaws are somewhat crushed; of the vertebral column, a great portion of the cervical and caudal regions has the bones in connexion; but the dorsals are much dislocated, and the ribs displayed. anterior right, and the left hinder extremity, are almost entire: the corresponding paddles are imperfect, and somewhat displaced. The pectoral arch is not seen, but the "sterno-costalarcs," that protected the abdomen, are perceptible. Of the pelvis, the principal bones remain; the caudal vertebræ and their hæmapophyses are beautifully shown.

A good idea of the general form of the living Plesiosaurus is conveyed by this fine specimen; and the correctness of the restoration of the entire skeleton given by Mr. Conybeare, (Pl. XLIX. of the same vol.) has been established by subsequent discoveries, and especially by the perfect examples which the researches of Mr. Hawkins have brought to light. I subjoin a few remarks from the original Memoir, and some additional details of the structure of these marine saurians.

"The neck is fully equal in length to the body and tail united; and which, surpassing in the number of its vertebræ that of the longest-necked birds, even the Swan, deviates from the laws which were heretofore regarded as universal in quadrupedal animals and the cetacea. The whole vertebral column numbers about 90 joints, viz. 35 cervical, 6 anterior dorsal, 21 dorsal and lumbar, 2 sacral, and 26 caudal. The proportion of these parts will stand nearly thus; taking the head as 1, the neck will be 5, the body 4, and the tail 3: the whole length being 13 times that of the head.

"The general proportions of the Tortoise, its length of neck, shortness of tail, and the smallness of its head, are in some degree analogous to what we observe in the Plesiosaurus; but the structure of the head and teeth of the latter, and its want of shell, entirely negative the idea of its being intimately allied to the chelonians, and decidedly connect it with the saurian order."

The vertebræ are recognised by their nearly flat articular facets, and the presence of two small vascular pits on the

inferior aspect of the centrum; and they are rather wider than long. The annular part is united to the body by suture, but not anchylosed to it. The spinous process is rather elevated; the posterior zygapophyses are higher than the anterior, and rest almost horizontally on those of the contiguous vertebræ.

The anterior cervical vertebræ support small ribs, which are articulated by two tubercles, and terminate in a hatchet-form, like the analogous elements in the Crocodile. In the six succeeding vertebræ, the ribs are elongated, and assume by degrees the form of the dorsal costal-processes.

The vertebræ of the tail are distinguished by the small facets for the hæmapophyses, which, as in the crocodiles, are articulated between the junction of two vertebræ, so that there are two articular depressions for each of the laminæ, the centrum having four, viz. two at the anterior edge and two at the posterior; the transverse processes of the caudals are attached by suture as in the young crocodile.

The humero-pectoral arch in the Plesiosaurus is very remarkable for the great size, and antero-posterior expansion of the coracoids, (see Lign. 73).

The structure of the ribs is also peculiar; for each pair of costal processes formed an osseous cincture, which encircled the body, and was composed of five distinct parts; namely, the two spinal, which were articulated to the centrum by a bifurcated head; and three slender vertical bones that were fitted to one another by oblique grooves; the median piece being transversely elongated, and slightly curved and pointed at both extremities; these intermediate processes are termed by Mr. Conybeare the "sterno-costal arcs;" a similar structure exists in the Chameleons and certain species of Iguanas. This mechanism admits of great expansion of the abdominal muscles and integuments during the inflation of the lungs; and hence M. Cuvier suggested the probability that the pulmonary organs in the Plesiosaurus were very large, and that this marine saurian, like the Chameleon, changed the colour of its skin according to the varied intensity of its respiration.

The principal bones of the anterior extremities, or paddles, consist of the usual normal elements, viz. a humerus, radius, and ulna; the first is a stout bone, with a rounded head, and

has the distal extremity expanded to articulate with the short flat bones of the fore-arm; the carpus or wrist is composed of a double row of from six to eight discoidal ossicula, which support the slender elongated metacarpals, that articulate with the digital or phalangeal bones; the latter are connected by flattened surfaces. The entire series of bones was, doubtless, enveloped in one common integument, in like manner as the paddles of the cetacea.

The pelvis, which is well shown in the specimen before us, consists of strong and short iliac, and broad pubic and ischiac bones; the two latter being expanded in the antero-posterior direction, like the coracoids.

The hinder paddles are very similar in their construction to the anterior, which they equal in size.

PHYSIOLOGICAL INFERENCES.-Mr. Conybeare concludes his admirable memoir with the following general remarks on the habits and economy of this tribe of marine saurians :—

"In its progression the Plesiosaurus must have more nearly resembled the Turtles than any other reptiles. That it was aquatic is evident from the form of its paddles; that it was marine is almost equally so from the remains with which its bones are universally associated ;' that it may have occasionally visited the shore, the resemblance of its extremities to those of the turtle may lead us to conjecture, but its motion must have been very awkward on land: its long neck must have impeded its motion through the water, presenting a striking contrast to the organization which so admirably fits the Ichthyosaurus to cut through the waves. May it not, therefore, be concluded, since, in addition to these circumstances, its respiration must have required frequent access of air, that it swam upon or near the surface, arching its long neck like the swan, and occasionally darting it down at the fish which happened to float within its reach? It may, perhaps, have lurked in shoal water along the coast, concealed among the sea-weed, and raising its nostrils to a level with the surface from a considerable depth, may have found a secure retreat from the assaults of its enemies; while the length and flexibility of its neck may have compensated for the want of strength in its jaws, and its incapacity for swift motion through

1 Remains of Plesiosauri have since been discovered in the Wealden formation. See "Fossils of Tilgate Forest," Pl. IX.

"the water, by the suddenness and agility of the attack which they enabled it to make on every animal fitted for its prey that came within its extensive sweep." 1

PLESIOSAURUS HAWKINSII.-Wall-case D.-The splendid specimen thus labelled (Lign. 73) in the upper compartment of this Case, was one of the earliest examples placed before the scientific world by Mr. Hawkins, as evidence of his consummate skill, and untiring patience and perseverance, in developing the enaliosaurian skeletons from the liassic deposits of England. This fossil, beautifully perfect as it now appears, was reduced to fragments in removing it from the stratum in which it was discovered, and as in the instance of the Maidstone specimen, would have thrown no light on the structure of the original animal, but for the successful result of the labour bestowed on its reparation.2

1 "Geol. Trans." vol. i. new series, pp. 388, 389.

2 The following account of the discovery of this specimen is too graphic and characteristic to be omitted. Premising that the specimen named as above by Professor Owen is described by Mr. Hawkins as Plesiosaurus triatarsostinus, I give the following extract from the "Memoirs of Ichthyosauri and Plesiosauri, extinct monsters of the ancient earth," by Thomas Hawkins, Esq. F.G.S.*

"I was spending the winter of 1831, as usual, in London—the pestilence came just in time to drive me thence to Somerset, for the salvation of the Triatarsostinus. Listen, reader! December gave up the ghost amidst a thousand frightful rumours of the coming cholera if I remember right, the first of January, 1832, is mournfully distinguished as the day on which one of the morning papers announced the scourge' present in Southwark. Who will ever forget the panic that followed? London was comparatively deserted within twenty-four hours. Tuesday six cases were bulletined as having occurred since its breaking out-a distinguished physician assured me that 600 were nearer the truth; along the Borough bank of the Thames, in those crowded houses, what havoc and death!

"Wednesday fatal cases trebled-about twenty were publicly acknowledged at least a hundred and twenty known to the intelligent few. Ah! I was smoking cigars on the box of the Bath mail all the night, and at ten o'clock, Thursday, galloping over the Mendips-the British Alps-on "the Exeter." The first thing that I ever do when I come to Glastonbury, is to call on my friend-my Pythias-there: the second, to drink a cup of coffee as sedative after my 140 miles journey; the third is to dash over to the lias quarries at a neck-hazard tangent. Now

* In one vol. royal folio, with numerous beautiful plates, 1834. Copies of this splendid and scarce work may be obtained of Professor Tennant, 149, Strand.

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