20

PALAEONTOLOGY.

than ordinary Saurians, and resembled in character the large terrestrial mammalianquadrupeds of the present epoch. Of British Oolitic strata, the Stonesfield slate,Bath oolite, Cornbrash, and Wealden have produced specimens of this genus. TheHylseosaurus and Iguanodon are both from the Wealden, the latter having beendiscovered by Dr. Mantell , and called Iguanodon by Conybeare from the resemblanceof its teeth to those of the living Iguana, though in other anatomical characters it isstrongly distinguished from it. From the supposed analogies between this reptileand the Iguana, it was estimated that the Iguanodon might he from 75 to 100 feetin length, but Professor Owen, on apparently sounder principles, deduces the lengthof 28 feet, a magnitude still entitling it to the appellation of enormous reptile. Aconsideration of this wonderful group of animals must fill the mind with admirationat the creative intelligence and power of the Supreme Originator of all things. Thisextraordinary development of reptile forms has been ascribed to a defectivecondition of the atmosphere, but, although the existence of land mammals negativessuch a supposition, there appears to be reason in the opinion of Professor Owen thatthese gigantic reptiles may have supplied the place of the large predaceous mammalsof the present world. Be this, however, as it may, the Oolitic fauna,—with its Marsu­ pials associated with the genus Trigonia of conchiferous Molluscs, (as at the presentepoch they are in Australia , the land of Marsupials, ) with its Belemnites and Ammo-nites, many of large size, its insects, and above all with its gigantic reptiles, whichpeople the land, the sea, and the air,—must always be distinguished amongst therecords of extinct worlds, for its singularity and grandeur.*

q, r,f Cretaceous Period .—Although the mind must long linger with delight on theextraordinary fauna which the Oolitic period has placed before it, the interest whichthe Cretaceous fauna is calculated to excite is of no ordinary kind. It is here thatthe remains of Birds are first distinctly recognizable in the Cimoliornis Diomedeus, orlong-winged bird of the Chalk ; a fact which from the imperfection of the specimenscould only have been established by the anatomical skill of Owen, who considers thatthe bird approaches nearest to the Albatross , though probably greatly exceeding it insize. As in the case of the scanty remains of Mammals discovered in the Oolite, theoccurrence of even one specimen of a bird of recognizable type must be accepted assufficient evidence of a more complex and complete fauna than could be inferred fromthe remains of aquatic animals alone, and the rarity of such specimens needs no otherexplanation than the marine nature of the deposit in which they occur. In the generaMososaurus, Leiodon, and Raphiosaurus, the Lizard-Saurians are represented, andProfessor Owen states that below the Chalk he has not hitherto found any instanceof a reptile possessing vertebrae with an anterior cup and posterior hall, or theordinary ball and socket structure of existing species. Chelonians (Turtles and Tor-toises), which commenced in the Triasic and appeared also in the Oolitic period,occur in the Chalk, though not noted in the Table. They are referred by ProfessorOwen to the marine section, or to the true Chelone.

Referring now to the Cephalopodous Molluscs as the most characteristic of both theOolitic and Cretaceous periods, the Belemnites are continued from the Oolites inthe two genera Belemnites and Belemnitella, the latter being characteristic of theupper Chalk. In the Tetrahranchiate division, the genus Nautilus produces a con-siderable number of species, and D’Orbigny gives as a characteristic difference betweenthose of the Oolitic period and those of the Cretaceous , that in the former there are

* Dr. Mantell'has recently discovered portions of a terrestrial Saurian, which he considers distinctfrom those previously described in the Oolitic strata. He calls it Pclorosaurus, or Monster Saurian,and estimates its length at about 80 feet.