576 BRITISH FOSSIL REPTILES. 



representing a trochanter [b], from which a thick rough ridge is continued, graflually 

 subsiding upon the shaft. 



The breadth of the proxunal end of the bone is 1 foot 1 inch ; at I foot distance 

 from that end the shaft is contracted to a breadth of 8 inches, and at its middle part to 

 one of inches. Notwithstanding the posthumous pressure which has shattered this part 

 of the crust of the femur, one may infer that tlie shaft was naturally subcompressed 

 from before backward. 



At three fourths of the distance from the head of the bone the shaft again begins to 

 expand, attaining at the distal end a breadth of 13^ inches. There is a distinct oblong 

 protuberance ( ) at the inner and back part of the shaft, 1 foot 6 inches beyond the 

 head, corresponding to that more developed prominence which has received the name of 

 ' third trochanter ' in lyuanodon and Scelkhmurm. There is also evidence of a 

 longitudinal ridge id) continued from the back part of the trochanter, about 9 inches 

 down the shaft, inclining toward the middle of the hinder surface. 



The popliteal cavity [e] is moderately concave, chiefly transversely through the 

 l)ackward production of the outer condyle {g). This is of less breadth posteriorly than 

 the inner condyle (/) but is more convex as well as more prominent. The outward 

 extension of the femur (/,) beyond this prominence is somewhat umisual. 



Tibia. — This bone is represented by its proximal end and three fourths of the 

 shaft (PI. 74, figs. 3 — 6). The shaft is more slender in proportion to the head than in 

 Ihjlceo- or Scelido- saurus, and yields a full subelliptic section (ib,, fig. 6). Part of the 

 articular surface for the inner femoral condyle may be recognised at a, and that for the 

 outer condyle at h, fig. 3, PI. 74. A ])rocnemial plate (c), ^Yith a base of 7 inches in 

 extent, projects forward 4 inches beyond the articular part of the head of the bone. As 

 wrought out of the matrix this plate shows a sharper free border than probably was 

 natural ; its obtusely rounded summit, ,i, has retained its condition as an epiphysis. The 

 diameter of the head of the tibia in the direction of the procnemial prominence («. <", fig. 5) 

 is 11 inches. The preserved longitudinal extent of the tibia is 2 feet. Tiie two 

 diameters of the fracture (/, fig. 3) are 4 inches 6 lines and 3 inches 6 lines. The 

 indication of a medullary cavity at the fracture (/) are hardly so definite as in fig. G, 

 and such as it is, the cavity was short ; for at the fracture («) the corresponding 

 central portion of the shaft shows an open osseous tissue with wide chondrosal 

 interspaces. 



In the obliquely fractured and partly crushed end of the shaft the trace of medullary 

 cavity has disappeared. The osseous tissue of the rest of the shaft is compact. Not- 

 withstanding the degree of crushing, the beginning expansion in the tibio-fibular 

 direction and of contraction or flattening in the rotulo-popliteal direction is unmistak- 

 able, and has led me to conclude that the distal, more flattened end of the bone is that 

 which is wanting in the present specimen. 



