24 



end, is a wide transverse parallelogram. This bone looks no little like 

 the distal end of a metapodial bone, but there are various reasons why 

 it is more probably femur or humerus. The form of the tibia espe- 

 cially determines it to be the former element. 



The head and distal end of the tibia, with six inches of the shaft, are 

 preserved. The former relates with the end of the femur, resembling it 

 both in size, simplicity of contour, and details of surface. The form is 

 crescentoid, one horn being the cnemial crest, the other posterior and 

 replaced by a short truncation. The inner (convex) face is rendered 

 angular by a median tuberosity, and all round this margin, shallow 

 grooves cut the solid angle at irregular distances. The articular face 

 displays the smooth area, and the shaft the delicate striae, seen in the 

 femur. The distal end is unsym metrically lenticular in section, one side 

 being more convex ; the articular face is rugose, showing a fixed liga- 

 mentous articulation for the astragalus. The convex face of the shaft 

 is coarsely striate-grooved near the extremity; on the other side the 

 intervening ridges are represented by exostoses or rugosities. The 

 flatter side becomes the more convex on the lower part of the shaft. 



Measurouents. 



M. 



Transverse diameter of condyles of femur .082 



Transverse diameter of shaft of femur 053 



( of middle of condyles .054 



Diameter fore and aft ^ of side of condyles 069 



( of shaft 038 



( greatest 102 



Diameter of head of tibia ^ fore and aft 096 



( transverse 060 



Diameter of shaft of tibia proximally i transverse. 050 



^ "^ \ lore and ait 04o 



Diameterdistalendof tibia | transvexsely 115 



( lore and aft 060 



Remarks. — If the bones above described as pertaining to the hind 

 limb are really such, they are smaller as compared with the dorsal ver- 

 tebrse than in SadrosaurusfoulJcei, and indicate an animal the size of 

 a horse. ' 



POLYONAX, Cope. 

 Char. Gen : 



A species considerably larger than the last, represented by vertebrae 

 and numerous fragments of limb bones. The most characteristic of the 

 former are two probably from the posterior dorsal region, which are 

 somewhat distorted by pressure. The more anterior is shorter than the 

 other, and exhibits both articular faces slightly concave, the one more 

 so than the other. They are higher than wide, and the border is scol- 

 loped above for the capitular articulation for the rib. There are numerous 

 nutritious foramina, and some ligamentous pits on the articular surfaces. 

 The inferior face is rounded. In the longer vertebra both faces are more 

 strongly concave, and at each end of the lower side there is an obtuse hypo- 

 pophysial tuberosity. The sides of thecentraof both vertebrae are concave. 

 The neueral canals are relatively small, and the neurapophyses co-ossified. 

 A third vertebra without arches, is similar in specific gravity, though with- 

 out the white surface-layer of the others. It is appropriate in size and 

 form to this species, and is peculiar in its flat form, resembling the ante- 



