656 
MR. J. W. HULKE ON THE POLACANTHUS FOXII. 
Tlie osseous tissue of all the vertebras is coarse, and the outer surface wants the 
closeness of texture and the smoothness so observable in Iguanodont bones. This 
textural difference serves to distinguish very mutilated pieces. It is not peculiar to 
this particular skeleton, for it is equally apparent in a thoracic vertebra which I dug 
a quarter of a mile to east of the place where this skeleton was discovered—a distance 
which makes it almost impossible that it should have ever formed part of it. 
Ribs .—Many of these show a double vertebral articulation by head and tubercle. 
In those referable to the front of the chest, as has been already mentioned, the head of 
the rib is very swollen and the neck is relatively slender. These parts are wanting in 
all the disconnected ribs from this part of the chest, but they are fortunately pre¬ 
served in situ upon three vertebrae (Plate 70, figs. 1 and 2). In this region the neck of 
the rib is short, and it joins the body of the rib in an almost uniform curve. In ribs 
referable to the middle of the trunk a very decided angle marks the junction of the 
Tubercle and body (Plate 76, fig. 2 ). In all ribs with double vertebral articulation the 
neck is slender, and it is so compressed that the long diameter of its cross-section is 
vertical. Beyond the tubercle the upper border (here become outer) expands so widely 
as to deserve the term “surface,” whilst the lower (here inner) border continues thin. 
This gives a triquetrous form and great strength to this part of the rib. 
Limbs. —The femur (Plate 74) is remarkable for the largeness of its articular extre¬ 
mities and the slenderness of its shaft. Both ends are much damaged by pressure. 
My description is taken from the right, which is better preserved than the left. The 
proximal end bears at its inner angle a sessile sub-hemispherical head (cap.), external 
to which and nearly in the same level with it is a well-developed trochanter ( tr.m .). 
The inner or posterior trochanter (fig. 2 , tr.i.), characteristic of dinosauria, is also 
strongly developed ; it is rather nearer to the proximal than the distal end of the bone. 
The knee condyles are very large; the inner is somewhat the larger of the two ; a 
deep narrow groove separates them in front, and a wider, relatively shallow, depression 
divides them behind. The length of the right femur is 55 - 5 centims. ; the diameter 
of the distal end across the condyles is 15*5 centims., and that of the prox im al end 
is 18 centims. The diameters of the caput femoris are 9 centims. and 8 '5 centims., 
and that of the middle of the shaft is 8 centims. 
The Tibia (Plate 75, figs. 1 ,. 2 ), the left one, is much shorter than the femur, being 
only 35 centims. long. It resembles the femur in the largeness of its joint ends and 
the slenderness of its shaft. The proximal end, distorted by pressure, shows obscurely 
a division of the articular surface into two parts answering to the femoral condyles (ccl ), 
and a remarkably large prsecnemial process (pro.). The distal end, flattened, is of the 
usual dinosaurian pattern, having a longer and narrower outer and a shorter and stouter 
inner division. When the bone is held vertically so that a line drawn between the 
proximal condyles is directed forwards, the longer axis of the distal end intersects 
this, making with it an angle of about 60°. This different direction of the ends makes 
the shaft appear twisted. Relatively to the large size of the articular ends the shaft 
