20 AMERICAN PERMIAN VERTEBRATES 



Among other vertebrates I know of nothing to compare with this 

 condition of the pineal vacuity, unless it be Casea; that the 

 chamber lodged some part of the brain substance there would seem 

 to be no doubt, possibly a part of the mesencephalon ; if it lodged 

 the pineal body only then it would seem very probable that the 

 organ was functional. The surface of the parietal and frontal 

 bones on either side of the brain surface and pineal chamber is 

 entirely smooth, with no indications for sutural attachment of the 

 descending plates described by Case. 



Among the material acquired later there is a quadrate bone, 

 but so very different in structure from that of either the Pariotichidae 

 or Pelycosauria that I cannot understand it. 



Of the limb bones I find four, all rather closely associated with 

 the type, and doubtless the ones referred to by Marsh in his original 

 description. They agree so closely in size and appearance that it 

 is very probable they belonged to the one individual and that prob- 

 ably the type of the genus and species. I find no others in the 

 collections which I can refer positively to Nothodon, though a 

 fragmentary femur and a fragmentary humerus may belong here. 

 The bones preserved are quite characteristic of the Diadectidae 

 short, heavy, and stout. The left tibia, shown in Plate XXXV ; 

 Fig. i, is a very stout, short bone; its outer border is deeply con- 

 cave and rather thin, less so than the inner and less thickened; 

 the distal articular surface is crescentic in outline, the inner horn 

 the thinner; the ventral surface is more deeply concave than the 

 dorsal; the shape of the proximal articular surface is shown in the 

 plate. 



The left fibula (Plate XXXV, Fig. 2) has the upper articular 

 surface oblique, and the lower end is much expanded; there is a 

 marked protuberance near the outer distal border; it seems to be 

 normal. 



The left radius and the left ulna (Plate XXXV) from their 

 association may belong in the same forearm. The radius is nearly 

 symmetrical in shape, the lower extremity a little more expanded 

 than the upper; the upper articular surface, somewhat compressed, 

 is sub triangular in shape; the lower transversely oval; its inner 

 border is a little thinner and a little more deeply concave than the 



