1884.1 ^* [Cope. 



present character by a process of degeneration. The origin of the Yerte- 

 brata is as yet entirely unknown, Kowalevsky deriving them from the 

 Tunlcata, and Sempa from the Annelida. 



Aves Mammalia 



Reptilia 

 Hyopomata Batrachia 



Selachii Ichthyotomi Dipnoi 



Holocephali 



Marsipobranchi 

 Leptocardi 



EXPLANATION OF PLATE. 



Fig. 1. Clepsydrops leptocephalus Cope, right quadrate bone (Q) with 

 condyle and zygomatic process {z) from the right, or external side Pi, 

 pterygoid bone of same side disphiced so as to be in plane of quadrate, 

 and to be seen from inferior side. One-lialf natural size. 



Fig. 2. Columella auris of the Individual of Clepsydrops leptocephalus 

 represented in fig. 1 ; internal side. Fig. 3a external side ; 2b proximal 

 extremity ; 2c distal extremity ; s, head of stapes ; Ecol. eplcolumella ; 

 d, distal articular surface, especially represented in fig. 2c. All figures 

 are half natural size, excepting 2c, which is natural size. 



Fig. 3. Left half scapular arch of a Pelycosaurlan, less clavicle and 

 episternum, one-half natural size, sc, scapula ; cl, facet for clavicle ; cor. 

 coracoid ; ec, epicoracoid ; s, open suture between coracoid and eplcora- 

 coid, indicating the immaturity of the animal. 



Fig. 4. Dorsal vertebra of a species of Embolophoius, one-half natural 

 size ; right side ; a, from front ; b, from below ; ic, intercentrum ; ca, 

 capitular rib articulation. 



Fig. 5. Astragalus of individual figured in flg. 4, one-half natural size ; 

 from below, ca, ca, facets for calcaneum ; na, do. for navicular; lib, 2, 

 do. for bone of spur, or os tlbiale. 5a, same bone from external or cal- 

 caneal border ; /, fibular facet. 56, same bone, proximal or fibular ex- 

 tremity. 



Fig. G. Left posterior foot of ClejjSydrops natalis Cope, superior side, and 

 Qn, inferior (plantar) side, two-tliirds natural size, as, astragalus ; ca, cal- 

 caneum ; na, navicular bone ; cu, cuboid ; euc, mc and ecc, eutocuneiform, 

 mesocuneiform and ectocuneiform bones, respectively. L H, IH, IV, V, 

 metatarsals. Tib 1, Probable tibial facet. In this specimen the calca- 

 neum is displaced ; being turned backwards, so as to present its two as- 

 tragalar facets [asf) anteriorly. 



