The Flying Lizards of the Secondary Rocks. 449 



ful flight than, is now enjoyed by any bat ; and the Pterodactyles 

 may at least have been as capable of migration as the great 

 frugiverous Gh iroptera. 



" The structural affinities, however, of the Pterodactyles to 

 the cold-blooded air-breathers, and their analogy in wing struc- 

 ture to the bats, indicate that they might have possessed the 

 faculty of becoming torpid, and of so existing during a period 

 when their food in a given locality was not attainable.''' 



In the smaller species (as fig. 1) the weakness of the pos- 

 terior extremities is less apparent, but in larger ones (as fig. 2) 

 the increase in length of the fore-arms is not followed by a 

 proportionate strengthening of the hind limbs ; on the contrary, 

 they seem to become attenuated as if from disuse. The pelvis 

 in Pterodactyles is very feeble, and (as in recent sauria) seems 

 to be anchylosed to not more than three sacral vertebras. 



The leg is composed of femur and tibia (with traces of a 

 fibula?). The tarsus can also be made out in some specimens. 

 The hind foot seems composed, in some species, of four toes 

 only, not five,* supported upon long and slender metatarsals, 

 and numbering 1, 2, 8, and 4 joints respectively, as in the 

 digits of the forehand. 



In RhamphorhyncJms (fig. 2) the false ribs are extended 

 as if for the attachment of the wing membrane, for which the 

 feeble pelvis and hind limbs seem but ill adapted. 



We have presented to us in this genus probably the most 

 remarkable form of all the Pterodactyles, one furnished with 

 a long stiff tail, exceeding the entire length of its body. It is 

 impossible to examine this singular prolongation of the caudal 

 vertebras, which is embedded in a compact mass of minute ossi- 

 fied fibres (as shown in our figure of the natural size), without 

 being at once impressed with the conviction that its use was 

 analogous to the long tail-feathers of the frigate bird, acting 

 not only as a powerful rudder (especially if it was furnished 

 with a crested fold of membrane, as in the tails of many recent 

 sauria), but also as an equipoise to the long and pointed 

 wings, which in life must have measured more than four feet 

 from tip to tip. The Rhamphorhynchus, when seated with closely 

 folded wings, would probably have presented a very similar ap- 

 pearance with that of this ocean wanderer. 



Beside the tiny Pterodactyle (fig. 1) there is another almost 

 equally small (P. MeyeriJ, which, amongst other interesting cha- 

 racteristics, possesses the circle of sclerotic eye-plates. These 

 bony plates occur in certain other reptilia, as the Enaliosaaria, 

 or sea lizards, and in turtles ; and are also found in many birds. 

 Their use appears to be "to vary the sphere of distinct vision, 



* In the restoration given of P. crassirostris by Goldfuss in Akad. der Wiss 

 (Joe. cit.) he attributes five toes to the hind limb. 



