138 AMERICAN PERMIAN VERTEBRATES 



Femur 104 A (Plate XXX, Fig. 4). — There are more than 

 twenty femora of this type, all of the same or nearly equal size, 

 conclusively indicating their adult character. The articular ends 

 are rather sharply edged, indicating more or less cartilaginous 

 surfaces, but not nearly to the extent characteristic of Clepsydrops. 

 The digital fossa is rather large; there is no distinctive trochanter or 

 adductor ridge. The shaft in the middle is nearly circular in cross- 

 section. The popliteal fossa is rather shallowly concave and broad. 



Tibia 104 B (Plate XXXIII, Fig. 8). — There are two complete 

 tibiae of this type, and parts of several others. They are, like the 

 larger tibia, shown in Plate XXX, Fig. 10, deeply concave on the 

 ventral side. The lower end is sharply truncate and transversely 

 oval. It is possible that this tibia belongs with femur 104 A, but it 

 seems to be too long. 



Tibia 104 C (Plate XXXIII, Fig. 7). — This type, of which I have 

 found but a single specimen, agrees so well with the larger form 

 provisionally referred to Clepsydrops that it may be merely a 

 juvenile specimen. Its proportions, however, are somewhat 

 different, but perhaps no greater than those observed between the 

 juvenile and adult femora referred to Clepsydrops. 



Fibula 104 D (Plate XXXII, Fig. 3). — A very slender right 

 fibula of peculiar form. The surface shown is nearly in one plane. 

 The upper articular surface is very oblique, as is seen in the photo- 

 graph, and is of an elongate crescentic shape. The external lower 

 surface turns backward and is gently concave, separated from the 

 convex dorsal surface by a rounded ridge. 



Fibula 104 E (Plate XXXIII, Fig. 9). — A second fibula of 

 precisely the same length as the preceding and of like slenderness 

 is quite surely of a different genus. The upper articular surface 

 is not oblique and the tibiale side is more concave in outline, nor 

 is the lower extremity at all like that of the preceding fibula, but 

 agrees better with that of the fibula of Varanosaurus. 



Fibula 104 F (Plate XXX, Fig. 9). — This fibula may possibly 

 be a juvenile form of that shown in Plate XXX, Fig. 11, and 

 referred provisionally to Clepsydrops, but the upper extremity is 

 twisted more obliquely to the shaft, the shaft on the concave side is 

 thinner, the lower border is more oblique to the axis of the bone, etc. 



