EDWARD D. COPE. 71 



has been made by the perching birds, whose feet have 

 become effective organs for grasping, whose vocal organs 

 are most perfect, and whose flight is generally good, and 

 often very good. In these birds also the circulatory 

 system is most modified, in the loss of one of the carotid 

 arteries. 



VI. THE MAMMALIAN LINE. 



Discoveries in paleontology have so far invalidated 

 the accepted definitions of the orders of this class that it 

 is difficult to give a clearly cut analysis, especially from 

 the skeleton alone. The following scheme, therefore, 

 while it expresses the natural groupings and affinities, 

 is defective in that some of the definitions are not with- 

 out exceptions : 



I. A large coracoid bone articulating with the sternum. 

 Marsupial bones : fibula articulating with proximal end of astragalus 



1. Monotremata. 



II. Coracoid a small process coossified with the scapula. 



(X. Marsupial bones ; palate with perforations (vagina double ; 

 placenta and corpus callosum rudimental or wanting ; cere- 

 bral hemispheres small). 

 But one deciduous molar tooth 2. Marsupialia. 



oca. No marsupial bones ; palate entire (one vagina ; placenta 

 and corpus callosum well developed). 



(5. Anterior limb reduced to more or less inflexible paddles, 

 posterior limbs wanting (Mutilata). 

 No elbow joint ; carpals discoid, and with the digits separated by car- 

 tilage ; lower jaw without ascending ramus 3. Cetacea. 



An elbow joint ; carpals and phalanges with normal articulations ; 

 lower jaw with ascending ramus 4. Siren ia. 



fi/3. Anterior limbs with flexible joints and distinct digits ; 

 ungual phalanges not compressed, and not acute at apex' 

 (Ungulata 2 ). 



y. Tarsal bones in linear series ; carpals generally in linear 

 series. 



1 Except the Hapalidte. 



2 Lamarck, Zoologie Philosophique. 1809. 



55 



