Cuvier commences his description with the fossil Trionyek and distinguishes—I, those from the gypsum-beds of the environs of Paris ; 2, those from the gypsum-beds of Aix ; 6, those from the 'inolasse' of the department of the Gironde ; 4, those from the gravel and clay-beds of Hautevigne in the department of the Lot and Garonne; 5, those from the gravel-beds in the neighbourhood of Castelnaudry; and 6, those from the sandy beds in the environs of Avaray.
He next considers the Emydeat, or Fresh-Water Tortoises, noticing 1, those from the Paris gypsum-beds ; 2, those discovered together with crocodiles in the Jurassic limestone of the neighbourhood of Soleuro ; 3, those of the femiginous sand of Sussex ; 4, those of the 'molasse' of La Grave and those of the 'molasses' of Switzerland ; 5, those from our Isle of Sheppey; 6, those from the environs of Brussels ; and 7, those from the manly sand (sable marneux) of the province of Asti.
The Marine Tortoises, or true Chelonians, he divides into—I, those of the environs of Maestricht; and 2, those of the slate of Glaris.
The Land-Tortoises noticed are—], those of the environs of Aix ; and 2, those found in the Isle of France under the volcanio beds.
The conclusions drawn by Cuvier are, that the Tortoises are as ancient inhabitants of the world as the Crocodiles; that they accom pany the remains of the latter generally ; and that as the greater number of their remains belong to fresh-water or terrestrial species they confirm the conjectures drawn from the bones of crocodiles as to the existence of isles or continents which were frequented by reptiles before the existence of viviparous quadrupeds, or at least before there was a sufficient number of these last to afford a quantity of remains at all comparable to those of reptiles.
Professor Owen, in his elaborate 'Report on British Fossil Reptiles,'—drawn up at the request of the British Association for the Advancement of Science, and published in their Transactions— gives the following account of the order Chelonia : I. Family Teat udinicke, Tortoises, or Land-Tortoises.
1. New Red-Sandstone Tortoises. The most ancient of the evidences of Chelonians in British formations appear to Professor Owen to be referrible to the Land-Tortoises ; and he quotes the foot prints from the quarries at Corncockle Muir, and those subsequently discovered at the quarries of Craigs, two miles east of Dumfries, as examples. I AMPHIBIA.) 2. Oolite Tortoises. Examples. Impressions of horny scutes about the size of those covering the carapace of a tortoise, ten inches in length, in the Oolite Slate of Stonesfield.
II. Family Emydicke, Fresh-Water Tortoises.
1. An undetermined species in the museum of Professor Bell, from the Eocene Clay near Harwich.
2. Emys testudiniformis, Owen (Emys de Sheppey, Cuv.?). Sheppey.
3. Platemys Bowerbankii, Owen. Sheppey.
4. Platemys Bultockii, Owen. Sheppey: 5. Tetrosternonpunctatum, Owen. Purbeck Limestone. N.B. Closely allied to Trionyx.
6. With regard to Platemys Mantelli (Emys de Sussex, Cuv., Emys Malvern, Gray), Professor Owen remarks that the fossils discovered by Dr. Mantell in the Wealden strata of Tilgate Forest, and the resemblance of which to the flat species of Emydian discovered by M. Hugi in the Jura Limestone at Soleure has been pointed out by Cuvier, are referrible to the pluroderal section of the Emydian family as arranged by Messrs. DumEril and Bibron, and in that section to the genus Platemys (Ilydraspis, Bell); but that not enough of the skeleton of any individual has yet been obtained to afford a foundation for specific character.
7. Large Emydian from the Kimrneridge Clay. A bone in the museum of Sir P. Grey Egerton, Bart., from Heddington Pits, probably belonging to a species of Platemys.
8. Footsteps of Emydians in New Red-Sandstone. Stourton Quarries, Cheshire.
With regard to the genus Professor Owen remarks that certain British fossils from the Secondary Formation referred to Trionyx have been proved to belong to another family of the supposed Trionyx from the New Red-Sandstones (Caithness) has been pronounced to be a ganoid fish (genus Coccosteus) by Agassiz. Nor bad Professor Owen wheu he wrote (1841) seen any Chelonite from the Wealden Formation that could be confidently affirmed to belong to Trionyx.
A femur from the Lisa at Linksfield in the possession of Mr. Robertson of Elgin, 41 inches in length, and found with remains of Plesiosaurus and Ifybodus, though not identical in form with any Trionyx with which Professor Owen could compare it, he found to resemble the modifications of the bone in that genus more closely than in Tortoises, Emydians, or Turtles. He remarks that although some of the Turtles of the Eocene period, as the Chelone longiceps, present such modifica tions of the jaws as seem to have adapted them to habits and food analogous to those of the Trionyx, yet evidences of this genus, to which the destruction of the eggs and young of crocodiles is more particularly assigned in the Nile and Ganges, are not wanting in certain localities where the London Clay appears to have been depo sited under circumstances analogous to those at the termination of equally gigantic rivers ; and he adds that unequivocal portions of a true Trionyx have been obtained from the Eocene Clay at Sheppey and at Bracklesham, and that they are also associated, as in the Paris basin, with remains of Anoplotherium and Palaotherium in the Eocene Limestone deposits in the Isle of Wight.
III. Family Chelonidce, Thalaasian Family, or Turtles.
1. Chelone planiceps, Owen. Portland Sandstone.
2. C. °borate, Owen. Purbeck Limestone.
3. Ais undetermined species of Chelone from the Wealden. Portions of the carapace, plastron, and bones of the extremities of a large species of Marine Turtle, some of them indicating individuals nearly three feet in length, discovered by Dr. Mantell in the Wealden strata of Tilgate Forest, are figured in the Doctor's 'Illustrations of the Geology of Sussex: This species, in Professor Owen's opinion, comes nearest to C. planimentum of the Harwich Eocene Clay.
4. C. pulchriceps, Owen. Superincumbent beds of the Lower Greensand ; Greensand near Barnwell, Cambridge.
5. C. Benstedi, Owen (Emys Benstedi, Mantell). Chalk ; Durham, Kent.
In a monograph on the 'Fossil Reptilia, of the London Clay,' by Professors Owen and Bell, published by the Palmontographical Society, the following species are described, and figures of the remains found, given.
Order-Chelonice.
Fainily-Marina.
Genus-as/One. • 1. C. brericeps (Emys Parkinsonii, J. E Gray ; Emys de Sheppey, H. V. Meyer ; Chelone antique, Konig). Eocene Clay of Sheppey.
2. C. longiceps. Eocene Clay of Sheppey.
3. C. cressicostata. Harwich Clay.
4. C. declivis. Eocene Deposits of Bognor, Sussex.
5. C. trigoniceps. Eocene Clay at Bracklesham.
6. C. cuniceps. London Clay of Sheppey.
7. C. subcarinata. Sheppey.