THE JURASSIC PERIOD. 247 



to the Birds, or as forming a class by themselves. The chief 

 points which separate them from Birds, as a class, are the 

 character of the apparatus of flight, the entirely different struc- 

 ture of the fore-limb, the absence of feathers, the composition 

 of the tail out of distinct vertebrae, and the general presence 

 of conical teeth sunk in distinct sockets in the jaws. The gap 

 between the Pterosaurs and the Birds has, however, been 

 greatly lessened of late by the discovery of fossil animals 

 \Ichthyornis and Hesperornis] with the skeleton proper to Birds 

 combined with the presence of teeth in the jaws, and by the 

 still more recent discovery of other fossil animals (Ptcranodon) 

 with a Pterosaurian skeleton, but without teeth; whilst the un- 

 doubtedly feathered Arch&opteryx possessed a long tail com- 

 posed of separate vertebrae. Upon the whole, therefore, the 

 relationships of the Pterosaurs cannot be regarded as absolutely 

 settled. It seems certain, however, that they did not possess 

 feathers this implying that they were cold-blooded animals ; 

 and their affinities with Reptiles in this, as in other characters, 

 are too strong to be overlooked. 



The Pterosaurs are wholly Mesozoic, ranging from the Lias 

 to the Chalk inclusive ; and the fine-grained Lithographic Slate 

 of Solenhofen has proved to be singularly rich in their remains. 

 The genus Pterodactylus itself has the jaws toothed to the ex- 

 tremities with equal-sized conical teeth, and its species range 

 from the Middle Oolites to the Cretaceous series, in connec- 

 tion with, which they will be again noticed, together with the 

 toothless genus Pterauodon. The genus Dimorphodon is Li- 

 assic, and is characterised by having the front teeth long and 

 pointed, whilst the hinder teeth are small and lancet-shaped. 

 Lastly, the singular genus Rhamphgrhynckus^ also from the 

 Lower Oolites, is distinguished by the fact that there are teeth 

 present in the hinder portions of both jaws; but the front por- 

 tions are toothless, and may have constituted a horny beak. 

 Like most of the other Jurassic Pterosaurs, Rhamphorhytuh&s 

 (fig. 179) does not seem to have been much bigger than a 

 pigeon, in this respect felling for below the giant "Dragons" 

 of the Cretaceous period. It differed from its relatives, not 

 only in the armature of the mouth, but also in the fact that 

 the tail was of considerable length. With regard to its habits 

 and mode of life, Professor Phillips remarks that, "gifted with 

 ample means of flight, able at least to perch on rocks and 

 scuffle along the shore, perhaps competent to dive, though not 

 so well as a Palmiped bird, many fishes must have yielded to 

 the cruel beak and sharp teeth of Rhamphorhynchus. If we 

 ask to which of the many families of Birds the analogy of 



