22 SIMOIQIIES IHN SIMQLIEIN IES, 
hind legs and for a short distance out upon the tail. The head 
was very bird-like, all the bones being closely united and the 
sutures between them disappearing early in the life of the 
animal. The skull was of many different forms in the different 
species and the jaws were almost always furnished with teeth, 
but in some of the more specialized of the genera these were 
absent. 
The group is generally divided into three families : 
Pterodactylide. 
Rhamphorynchida. 
Pteranodontide. 
_ Pterodactyide: forms with short tails; the skull quite long 
and furnished with teeth; the sides of the skull anterior to 
the orbits broken by vacuities that possibly aided in lighten- 
ing the weight of the skull. The orbits were large and there 
was only one temporal arch. The metacarpals were longer than 
one half of the length of the forearm. 
Pterodactylus was about a foot long and very slender in all of 
its proportions. The skull was long and bird-like and furnished 
with teeth at the anterior ends of the jaws only. There are 
many species of this genus known, the most of which come from 
the Upper Jurassic layers (Lithographic slates) of Germany, 
near Eichstat and Bayern. A few specimens have been taken 
from the Upper Jurassic of France in the department of Ain and 
the Kimmeridge clays of England have furnished isolated bones 
of the same genus. 
Rhamphorynchide : forms with long tails which are frequently 
accompanied by ossified tendons; the skull only moderately 
elongate; the jaws furnished with teeth throughout their whole 
length which grew smaller towards the posterior part of the jaw, 
those in front being long and slender. Metacarpals shorter 
than the half of the forearm. The fifth toe of the hind foot 
taking some part in the support of the wing membrane and 
showing a much greater development than the other toes. 
Dimorphodon, from the Lias of Lyme-Regis in Dorsetshire, 
England, was a much stouter form than the /rerodactylus,; the 
