All the groups of Jurassic Reptiles which we have hitherto been considering are wholly unrepresented at the present day, and do not even pass upwards into the Tertiary period.  It may be mentioned, however, that the Oolitic deposits have also yielded the remains of Reptiles belonging to three of the existing orders of the class-namely, the Lizards (Lacertilia), the Turtles (Chelonia), and the Crocodiles (Crocodilia).  The Lizards occur both in the marine strata of the Middle Oolites and also in the fresh-water beds of the Purbeck series; and they are of such a nature that their affinities with the typical Lacertilians of the present day cannot be disputed.  The Chelonians, up to this point only known by the doubtful evidence of footprints in the Permian and Triassic sandstones, are here represented by unquestionable remains, indicating the existence of marine Turtles (the Chelone planiceps of the Portland Stone).  No remains of Serpents (Ophidians) have as yet been detected in the Jurassic; but strata of this age have yielded the remains of numerous Crocodilians, which probably inhabited the sea.  The most important member of this group is Teleosaurus, which attained a length of over thirty feet, and is in some respects allied to the living Gavials of India.

[Illustration:  Fig. 181.—­Archoeopteryx macrura, showing tail and tail-feathers, with detached bones.  Reduced.  From the Lithographic Slate of Solenhofen.]

[Illustration:  Fig. 182.—­Restoration of Archoeopteryx macrura.  (After Owen.)]

The great class of the Birds, as we have seen, is represented in rocks earlier than the Oolites simply by the not absolutely certain evidence of the three-toed footprints of the Connecticut Trias.  In the Lithographic Slate of Solenhofen (Middle Oolite), there has been discovered, however, the at present unique skeleton of a Bird well known under the name of the Archoeopteryx macrura (figs. 181, 182).  The only known specimen—­now in the British Museum—­unfortunately does not exhibit the skull; but the fine-grained matrix has preserved a number of the other bones of the skeleton, along with the impressions of the tail and wing feathers.  From these remains we know that Archoeopteryx differed in some remarkable peculiarities of its structure from all existing members of the class of Birds.  This extraordinary Bird (fig. 182) appears to have been about as big as a Rook—­the tail being long and extremely slender, and composed of separate vertebrae, each of which supports a single pair of quill-feathers.  In the flying Birds of the present day, as before mentioned, the terminal vertebrae of the tail are amalgamated to form a single bone ("ploughshare-bone"), which supports a cluster of tail-feathers; and the tail itself is short.  In the embryos of existing Birds the tail is long, and is made up of separate vertebrae, and the same character is observed in many