ON THE BONES OF THE HIPPOPOTAMUS. 385 



its ischium is transverse, and in a right line with its corresponding one. 

 In the OX, thej' form together an angle of 45 degrees ; in the hippopo- 

 tamus they are almost parallel. 



The OS sacrum, a b {ib.^, is very large ; the external part of the os 

 ilium, c d,\s verymuch widened, and almost in the same plane. The part 

 situated towa,rds the back of, or rather above, the os sacrum rises gently. 

 The neck of the bone, e e, is broad and .short, and the bone itself is more 

 broad than long; its external edge is as long as the internal ; its posterior 

 surface is concave ; what we can see of the anterior, witliout displacing 

 the OS sacrum, is plane. The pubes, f s, a,re not strongly defined, so 

 that the cavity of the ])elvis is small. The antero-posterior diameter, 

 g h, is nevertheless longer by a third than the transverse, i k. Th.6 

 perspective renders it difficult to judge of this proportion. 



The shape of the anterior strait is oblique towards the back part. 

 The posterior part of the ischium, m m, is very much enlarged. 



The femur, K K (plate St^, fig. 1, and plate 31, figs. 15, 16, and 17), 

 is finely and straightly shaped. Its shaft is almost even from top to 

 bottom, regularly cylindrical in front, with two sharp lines, an internal 

 and a posterior, slightly marked. Its great trochanter, a, com.pressed at 

 the sides, does not surpass the height of its head, b ; the smaller, c, is 

 moderate ; they form a junction by an oblique salient rib, in front of 

 which is a deep and rounded fossa. There is no third, as in the 

 rhinoceros, the tapir, and the horse. The lower extremity is very 

 thick. The internal condyle is larger by one third than the other. 

 They are both rather prominent behind. The pulley of the rotula, d, 

 is not very deep, its edges are rather blunt. The internal rises higher 

 than the external. 



It does not resemble any but the femora of the great ruminants ; but 

 its upper head is much more detached, more spherical, and the inferior 

 is larger, particularly at the back part. 



The?e differences will be of use in enabling us to distinguish it from 

 the femur of the ox : that of the giraffe, which might more easily mis- 

 lead us, as being of the same size, besides having its upper head closer to 

 the body, has moreover its condyles smaller, and the internal edge of 

 the pulley of the rotula much more elevated and more salient : the 

 femur of the pig bears a great resemblance to it in its upper part, 

 but much less in its lower; and, besides, its dimensions do not admit 

 of the possibility of a mistake. 



The tibia, L L, (plate 30. fig. 1, and plate 31, figs. 18 and 19), is 

 shorter and thicker than that of any known animal, particularly at the ex- 

 tremities ; it is triangular throughout ; however, its anterior edge, a b, 

 w'hich is very prominent in the two thirds of the upper part, and slanted 

 at the top, has a defection at the base towards the internal malleolus, b. 

 The external malleolus is formed, as in the pig and in the ruminants, 

 by apeculiar little bone, c, which articulates with the fibula, the tibia, the 

 astragalus, and a particular facette of the calcaneum. The superior 

 head has a very curious shajDC, being rounded into a semicircle on the 

 internal side, deeply sloped towards the back and on the front of the 

 external side. The external condyle is almost square; the internal is 

 larger and triangular ; the anterior edge forms, in front of the slope on 

 the external side, a large rounded tuberosity. The surface of the astra- 



