ritOF. II. (i. SKKLEY ON AGKOSAUKUS MAC(i ILLIVRAYI. 1G5 



contour. The width proximally of the antcro-internal surface is 

 about f) cm., but it narrows rapidly. The posterior contour of 

 the shaft is concave. 



The surface of the bone at the proximal end is moderately concave, 

 with a slight vertical channel for the fibula towards the external 

 crest. This is augmented by crushing, in the left tibia, but the 

 imperfect proximal end of the right tibia shows no post-mortem 

 comj)ression. 



The slender portion of the shaft includes more than its middle 

 third, and is more attenuated than in any Saurischian hitherto 

 figured. Its section is ovate, and the boue appears to be thin and 

 hollow. 



The distal end expands gradually, so that there is no point in 

 which it is sharply defined from the shaft ; it is about half as deep 

 as the proximal end. The articular surface is more quadrate than the 

 distal end of any Saurischian tibia figured, with the exception of 

 Dimodosauriis poligniensis, in which the proportions are similar. It 

 is 3 cm. wide, and measures rather more in depth, with two pairs of 

 sides nearly parallel, though the lateral borders converge a little 

 forward. A deep notch indents the anterior margin in the middle, 

 and marks a division of the basal surface which descends on the 

 fibular side like a broad talon and indicates a corresponding modifica- 

 tion of the astragalus- I infer from the quadrate shape of the 

 articulation that the distal end of the fibula was carried external 

 to the tibia, and not in front of it as in Ornithischia, which have the 

 distal end of the tibia expanded transversely. The somewhat saddle- 

 shaped articular surface is clean, and gives no indication of close 

 union with the astragalus. 



Another fragment may be the distal end of the fibula ; it is less 

 than 5 cm. long, with a slender shaft 1 cm. in diameter as preserved. 

 The articular surface is oblique, flattened, and measures 2'o cm. in 

 width by 1'8 cm. in depth ; it is convex on the tibial side, and less 

 convex externally. 



A fracture in the matrix displays two claws, which are flattened 

 and appear to be compressed from side to side. They are of the 

 type which is usual in carnivorous reptiles. The larger of them is 

 2*5 cm. long and 1*8 cm. deep at the slightly concave articular 

 border : the contour of the bone is convex above and concave below. 

 The smaller claw is more slender ; it is 2 cm. long, and 1*3 cm. 

 deep at the posterior articulation. 



The distinctive character which determines the afiinities of the 

 fossil is the distal end of the tibia. It shows an ordinal resemblance 

 with Poehiloplearon and Cetiosaurus, but with Dimodosaurus from the 

 top of the Keuper its resemblance is so close that the two must be 

 regarded as nearly allied. I consider the fossil now described as 

 generically distinct from Massosjwndijlus and all known types, and 

 defined by its slender shaft, by the enlarged proximal end which curves 

 backward, by the slight development of the cncmial crest, by the 

 uniform increase in size of the distal end, and finally by the moderate 

 excavation of the distal articulation on the inner side. The remains 

 indicate an animal about as large as a sheep. 



