Synopsis of the Families of Vertebrata. 
Nine orders of Reptilia are known. 
I. The quadrate bone united with the adjacent elements by 
A. Cranium with one postorbital bar. 
a A paroccipital bone. 
A supratemporal bone ; ribs two-headed on cent- 
rum; carpals and tarsals not distinct in form 
from metapodials ; Ichthyopterygia. 
No supratemporal ; sub- and post-pelvic ossifica- 
tions; interclavicle and clavicles separated 
from and below scapular arch ; ribs one- 
headed ; coracoid large, free ; Testudinata. 
aa No paroccipital bone. 
Ribs mostly two-headed, capitulum intercentral ; 
clavicles and interclavicles forming part of 
shoulder-girdle ; no sub- or post-pelvic bones ; 
pelvic elements below plate-like , obturator 
foramen small or none ; Theromora. 
Ribs one-headed; scapula triradiate ; no clavicles ; 
coracoid large, distinct; no sub- or post- 
pelvic bones ; Plesiosanria. 
AA. Cranium with two postorbital bars. 
«. No paroccipital bone ; (no supratemporal). 
Ribs two-headed ; no interclavicle ; external 
digits greatly elongate to support a patagium ; Ornithosauria. 
Ribs two-headed; no interclavicle; acetabulum 
perforate ; feet ambulatory ; no patagium ; Dinosauria. 
Ribs two-headed ; an interclavicle ; acetabulum 
closed ; feet ambulatory ; no postfrontal bone ; Crocodilia. 
Ribs one-headed ; an interclavicle ; acetabulum 
closed ; feet ambulatory ; Rhynchocephalia. 
II. The quadrate bone loosely articulated with adjacent 
elements, and only proximally. 
