ON THE PHYLOGENETIC ARRANGEMENT OF 

 THE SAUROPSIDA. 



DR. G. BAUR, 

 Yalk Collegs Museum, New Haven, Conn. 



Cope^ has given the following classification of the Reptilia : — 



A. Extremities not differentiated in form beyond proximal 

 segment. 



I. Os quadratum immovably articulated to squamosal, etc. 

 Tubercular and capitular rib-articulations present and distinct. 



I. Ichthyopterygia. 



A.A. Elements of extremities differentiated. 



n. Os quadratum immovably articulated, capitular and 

 tubercular rib-articulations distinct. Archosauria. 



Pubis and ischium united, and with little or no obturater 

 foramen ; one posterior cranial arch ; limbs ambulatory ; a 

 procoracoid. 2. Theromorpha. 



Ischium and pubis distinct, the latter directed forwards, back- 

 wards, or downwards ; two posterior cranial arches ; limbs am- 

 bulatory; no procoracoid. 3, Dinosauria 



(+ Crocodilia) . 



Ischium and pubis united ; two postcranial arches ; anterior 

 limbs volant. 4. Ornithosauria. 



III. Os quadratum closely united to cranial arches ; but one 

 rib-articulation. Synaptosauria. 



Distinct hyposternal and postabdominal bones; ribs joining 

 each two vertebrae, and generally forming a carapace ; one pos- 

 terior cranial arch. 5. Testudinata. 



Hyposternal and postabdominal bones not distinct ; two pos- 

 terior cranial arches ; ribs attached to one vertebra ; a sternum ; 

 ? no procoracoid. 6. Rhynchocephalia. 



^ Cope, E. D. On the evolution of the vertebrata, progressive and retrogressive. 

 Amer. Naturalist, March, 1885, pp. 245-246. 



