400 



E. C. CASE 



rugose expanded apices of Zatrachys apicalis Cope, and so I 

 have referred this specimen to that genus until further informa- 

 tion may be obtained. Fig. 5. The fragment is .054™ in 

 height and .058"" across the lateral processes. 



DIADECTIDAE. 



The family Diadectidae is known so far from the skull, teeth, 



vertebrae, pelvis, 

 clavicle, and inter- 

 clavicle ; to this 

 we may add the 

 scapulae, if the 

 specimen de- 

 scribed above be- 

 longs, as assumed, 

 to this family. The 

 separation of gen- 

 era and species has 

 been done almost 

 entirely upon the 

 characters of the 

 teeth and skull, so that it has been impossible to determine accu- 

 rately the position of isolated bones. A specimen in the Chicago 

 collection (No. 62) makes it possible to add a description of the 

 caudal vertebrae, some of the bones of the limb and foot, and 

 especially the presence of an unsuspected structure, i. e., dermal 

 plates overlying the ribs and corresponding to them in number. 

 This last structure is shown in two separate fragments ; the 

 largest shows five ribs in place and the plates covering them. It 

 is impossible to say which side the fragment is from. The ribs 

 are quite stout and show a large medullary cavity. The plates 

 are large and thin. Their edges are broken away so that their size 

 cannot be determined. The plates lie one over the other like 

 shingles. The plate at one end has the end broken and turned 

 down. Near this is a separate fragment which may be either a 

 portion broken off from the edge of the plate or a distinct mar- 

 ginal plate. The approximate width of each of the plates is 

 .033™ and the length of the fragment is about .160™. 



Fig. 6. — Foot bones of a diadected reptile ; a and b 

 metacarpals {?); c, d, e, phalanges found united ; /, another 

 terminal phalange. 



