26o HISTORICAL PALEONTOLOGY. 



dence of footprints in the Permian and Triassic sandstones, are 

 here represented by unquestionable remains, indicating the ex- 

 istence 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 inhab- 

 ited 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. 



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 Connecti- 

 cut 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 

 Archaopteryx 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 pre- 

 served 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 Archaopteryx differed in some remark- 

 able 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 existing Reptiles. The 

 tail of Archaopteryx, therefore, is to be regarded as the per- 

 manent retention of an embryonic type of structure, or as an 

 approximation to the characters of the Reptiles. Another 

 remarkable point in connection with Archaopteryx, in which 

 it differs from all known Birds is, that the wing was furnished 

 with two free claws. From the presence of feathers, Archa- 

 opteryx may be inferred to have been hot-blooded; and this 

 character, taken along with the structure of the skeleton of the 

 wing, may be held as sufficient to justify its being considered 

 as belonging to a class of Birds. In the structure of the 

 tail, however, it is singularly Reptilian; and there is reason to 



