Further to the left, on the shore of the Secondary Island, is a restoration of the Plesiosaurus dolichodeirus, or Long-necked Plesiosaurus (No. 16). The head in this remarkable species is smaller, and the neck proportionally longer than in the Plesiosaurus macrocephalus. The remains of the Long-necked Plesiosaur have been found chiefly at Lyme Regis, in Dorsetshire. The well known specimen of an almost entire skeleton, formerly in the possession of His Grace the Duke of Buckingham, is now in the British Museum.
No. 17.—Plesiosaurus Hawkinsii.
The most perfect skeletons of the Plesiosaurus are those that have been wrought out of the lias at Street, near Glastonbury, by Mr. Thomas Hawkins, F.G.S., and which have been purchased by the trustees of the British Museum. A restoration is given by Mr. Waterhouse Hawkins, at No. 17, of a species with characters somewhat intermediate between the Large-headed and Long-necked Plesiosaurs, and which has been called, after its discoverer, Plesiosaurus Hawkinsii.
The Plesiosaurs breathed air like the existing crocodiles and the whale tribe, and appear to have lived in shallow seas and estuaries. That the Long-necked Sea-lizard was aquatic is evident from the form of its paddles; and that it was marine is almost equally so, from the remains with which its fossils are universally associated; that it may have occasionally visited the shore, the resemblance of its extremities to those of a turtle leads us to conjecture; its motion, however, must have been very awkward on land; its long neck must have impeded its progress through the water, presenting a striking contrast to the organisation which so admirably adapted the Ichthyosaurus to cut its swift course through the waves. “May it not, therefore, be concluded that it swam upon, or near the surface,” asks its accomplished discoverer, “arching back its long neck like a swan, and occasionally darting it down at the fish that 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 dangerous 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 the water, by the suddenness and agility of the attack which enabled it to make on every animal fitted for its prey which came within its reach.”[5]
For the Secondary Island three species of the Plesiosaurus have been restored, the Plesiosaurus macrocephalus, the Plesiosaurus dolichodeirus (Gr. dolichos, long, deire, neck), and the Plesiosaurus Hawkinsii. The name “long-necked” was given to the second of these species before it was known that many other species with long and slender necks had existed in the seas of the same ancient period: the third species is named after Mr. Thomas Hawkins, F.G.S., the gentleman by whose patience, zeal, and skill, the British Museum has been enriched with so many entire skeletons of these most extraordinary extinct sea-lizards.
The remains of all these species occur in the lias at Lyme Regis, and at Street, near Glastonbury; but the Plesiosaurus Hawkinsii is the most abundant in the latter locality.
NEW RED SANDSTONE.
“Trias” is an arbitrary term applied in geology to the upper division of a vast series of red loams, shales, and sandstones, interposed between the lias and the coal, in the midland and western counties of England. This series is collectively called the “New Red Sandstone formation,” to distinguish it from the “Old Red Sandstone formation,” of similar or identical mineral character, which lies immediately beneath the coal.
The animals which have been restored and placed on the lowest formation of the Secondary Island, are peculiar to the “triassic,” or upper division of the “New Red Sandstone” series, which division consists, in England, of saliferous (salt-including) shales and sandstones, from 1000 to 1500 feet thick in Lancashire and Cheshire, answering to the formation called “Keuper-sandstone” by the German geologists; and of sandstone and quartzose conglomerate of 600 feet in thickness, answering to the German “Bunter-sandstone.”