The skeleton is attached to the slab of stone by its dorsal aspect, consequently the under surface of the lower jaw, and the series of cervical vertebræ, is exposed. The pectoral arch, with its large coracoids and anchylosed scapula and clavicles, is well preserved; the humerus, radius, and ulna, of each side are in situ, and the right carpus, and some of the phalanges. The sterno-costal arcs of the abdominal region are beautifully shown; and the pubic and ischiac bones of the pelvis are clearly developed; there are no anchylosed sacral vertebræ in the Plesiosaurus. The femora, tibiæ, and fibulæ, and many of the tarsal and digital bones of the paddles, are likewise well defined; and the series of caudal vertebræ, though dislocated from the sacrum, and thrown out of the normal position, is very distinct. This specimen was figured and described by Dr. Buckland and other authors as Plesiosaurus dolichodeirus; but Professor "it happened that a person of Street, by name Creese, a quarrier, a worthy man enow, came across the Triatarsostinus a few days before, and as I had given him no inconsiderable monies for the bones that he had met with in the course of his business, he was at the pains of taking it home in hopes of getting more. The Philistines from Dan to Beersheba know what a vile tendency to mischief every beautiful object that he can set his paw upon disgraces John Bull."; Mr. Hawkins found that in the attempt to clear the specimen, the men had broken it into a hundred pieces, and lost many of the fragments. The narrative thus proceeds : "May heaven forgive me-magna componere parvis-I have never forgiven the Goths that sacked the Eternal City, the infamous Caliph that destroyed the Alexandrian library-nor these men! When I came to Street so opportunely, they had thrown away nearly the whole of the two anterior paddles, and the whole of the posterior right one-they had reduced the flag-stone to nearly thirty pitiful pieces, and stabbed the bone as a Spanish Matadore does a bull--all over. But I should congratulate myself upon such fortune as fell to my lot, and thank the stars and the cholera that it was no worse, as had I not arrived at that very four of the clock in the afternoon, Bruin had resolved to chissel away the surface of the stone, never dreaming that the process would have swept away the bones too! "Creese paid a severe penalty for his temerity: instead of giving him as much as my conscience told me was the worth of it-a rule that I have never departed from but in this deserving instance-I was content to pay him liberally for the trouble he had been at in noticing it. The rest of the chapter is short. Some parts of the three minor paddles are recovered. I forgot the pestilence, sat up at work all day and all night, and in about two months the Triatarsostinus, my hewn-god, was finished." Owen, in his masterly review of the osteology of the Enaliosaurians, has established its specific distinction, and assigned to it the name of its discoverer. There are three other remarkably choice examples of this species in Cases E and F. That in the latter case is the most exquisite fossil skeleton in the British Museum; the perfection of the bones, the admirable manner in which the stone has been chiselled away, and the graceful position of the neck, head, and limbs, render this precious relic invaluable. The specific characters which distinguish the Plesiosaurus Hawkinsii from the typical P. dolichodeirus, are chiefly differences in the relative proportion of various parts of the skeleton. The head is somewhat larger: it is three times the length of the neck, instead of being four times, as in P. dolichodeirus. The length of the neck only slightly exceeds that of the trunk, whereas in the latter it is equal to that of the united body and tail. The number of cervical vertebræ is twenty-nine; in P. dolichodeirus, thirty-five.' There are also recognisable differences in the forms and relative sizes of the ulna and tibia. PLESIOSAURUS ARCUATUS.-Wall-case D: and on the top of Wall-case E.-Many detached bones of this species are placed on each side the specimens above described in Case D. This species is distinguished by the development of distinct transverse processes, from the sides of the centrum of the vertebræ, for the support of the cervical ribs, especially from those of the posterior moiety of the cervical region. "These processes have the articular surfaces traversed by a longitudinal groove, as in other Plesiosauri, and, consequently, thus present the appearance of the two normal transverse processes 1 Cervical vertebra.-Professor Owen reckons as cervicals those in which the centrum or body of the vertebra bears the whole, or a part of the costal articular surface. "The body of a cervical may always be distinguished from that of a caudal vertebra in being without any trace of hæmapophysial pits. The dorsal vertebræ are those in which the costal surface is situated wholly on the neurapophysis. The caudal vertebræ are characterised by having both costal and neurapophysial impressions on the body, except the terminal ones, which are readily distinguished by their small size, the absence of both the above-named impressions, and by the concave character of their articular surfaces.""Brit. Assoc. Reports," 1839, p. 58. confluent at the base. The dorsal vertebræ are distinguished by the correspondingly great development of the transverse processes upon the neurapophyses." 1 skeleton, between four and five feet in length, from Lyme Regis, discovered and developed by the late Miss Mary Anning, was figured and described by Dr. Buckland under the name of P. macrocephalus, from the relatively great size of the cranium as compared with that of the typical P. dolichodeirus. A cast of this specimen was presented to the British Museum, by that eminent and zealous palæontologist, the Earl of Enniskillen; and the osteology of this species is fully elucidated by Professor Owen.3 The arched position into which the vertebral column has been thrown, presents the entire skeleton on a comparatively small area. The upper part of the cranium, with the orbits, and the jaws and teeth, are exposed. The cervical and dorsal vertebræ form a continuous, and but slightly dislocated series; the tail is imperfect; the anterior and posterior paddles of the left side are entire. The length of the neck exceeds that of the lower jaw only twice, instead of thrice as in P. Hawkinsii. The greater development of the head is associated with thicker and stronger vertebræ ; there are twenty-nine in the cervical region; the "Brit. Assoc. Rep." p. 75. 2 Dr. Buckland's." Bridgewater Essay," Pl. XIX. ROOM III. PLESIOSAURIAN REMAINS FROM THE WEALDEN. 351 vertebræ are shorter than in the species previously described, and approach in their proportions to those of the Ichthyosaurus: the processes of the cervical vertebræ are stronger. The dorsal vertebræ differ from those of P. Hawkinsii in the bodies being more flattened antero-posteriorly, and more concave laterally. Other osteological characters, establishing the specific distinction of this Plesiosaurus, are minutely detailed in the Reports so often cited. PLESIOSAURUS RUGOSUS.-Wall-case D.-This specimen of a very rare species of Plesiosaurus was discovered in the Lias near Belvoir Castle, and presented to the British Museum by the Duke of Rutland. It consists of the cervical region of the vertebral column, a considerable portion of the bones of the trunk, those of the four paddles, and some of the vertebræ of the tail; but the latter are much displaced. The cranium is wanting. Some detached Plesiosaurian vertebræ, readily distinguished from all others by the peculiarly rugous character of the free, or non-articular surfaces of the body, were ascribed to a distinct species, under the name of P. rugosus, in "Brit. Rep.” 1839; and other characters of these isolated bones were pointed out.' The discovery of the skeleton before us has confirmed the accuracy of the distinction. Among other peculiarities, Prof. Owen remarks, that the two costal impressions on each side the bodies of the middle cervical vertebrae are in this species completely divided, and by a wider and deeper groove; and they are situated near the lower margin of the vertebra. The contour of the articular surface of the vertebral body is almost circular, the peripheral border being convex, and leading inward to a concavity, and the centre of this surface is slightly convex. The absence of the cranium, and the dislocated state of the spinal column, together with the loss of many of the vertebræ, render it useless to give a more particular description. PLESIOSAURIAN REMAINS FROM THE WEALDEN.-Among the reptilian bones discovered in the strata of Tilgate Forest, were dorsal and cervical vertebræ of Plesiosauri, referable to one of the typical species previously described: probably the P. dolichodeirus some of them are figured in my "Fossils of Til 1 “Brit. Assoc. Rep." 1839, p. 82. 1 gate Forest." Several teeth, and specimens of the median bones of the sterno-costal arcs, and portions of coracoids of plesiosauri, have also been found in other localities. These remains were in the same fragmentary and waterworn condition as those of the terrestrial reptiles. The occurrence of the bones of this remarkable type of marine saurians in the freshwater formation of the south-east of England, may be attributable to the influx of the tidal waters into the ancient estuaries and bays; but it is also probable, from the presumed habits of the Plesiosauri, that the embouchure of the river of the Country of the Iguanodon was frequented by shoals of these reptiles, as well as by turtles and predatory fishes. Unfortunately, the bones of Plesiosauri collected by me, and transferred to the British Museum in 1839, are not yet placed so that they can be referred to in this volume; but the fact is worthy of record in relation to the history of the Wealden formation. ** In consequence of the arrangement of the fossils in this room, we must defer the consideration of the other group of Enaliosaurians, the Ichthyosauri, till the next chapter, and proceed to notice the contents of Wall-case G, which chiefly consist of an interesting series of mammalian and other remains, from the tertiary deposits of Central France. (See ante, p. 143.) 11 Vol. 4to. Published in 1827, Pl. IX. figs. 4, 5; Pl. XVII. fig. 20, r. 79. |