402 ON THE FOSSIL BONES OF PACHYDERMATOUS QUADRUPEDS. 



5. The Great Bones of the Posterior Extremity. 

 The Os Innominatum. — I brought two ossa innominata with me from 



Tuscany — one of the right, the other of the left side — both almost of 

 the same size as those of our skeleton of the living species — so much 

 so, that by placing them on their respective sides, the differences be- 

 came apparent in an instant : unfortunately the pubis is broken. 



The fossil (plate 37, figs. 1 and 2), has the two wings of the os 

 ilium more equal : the external does not exceed the other in size ; the 

 returning line, extending from the external spine to the cotyloid cavity, 

 is inflected like that extending from the sacrum to the ischium. In 

 the living animal the first is less inflected, thereby communicating an 

 obliquity and a defect of symmetry to the cs ilium, which are not 

 observable in the fossil. The cotyloid cavity of the fossil is, by one 

 fourth, larger than that of the living animal. The ischium is shorter 

 and much thicker. Its superior margin, at the spot where it enlarges, 

 is sharp in the living, and square in the fossil : its enlarged part is 

 not concave inside, and the upper part of its tuberosity deviates out- 

 wards ; while in the living animal it rises in a vertical direction, and 

 is parallel with that of the other side. In general, the os innomina- 

 tum of the fossil is thicker than that of the living animal. 



The Fossil Femur (plate 37, figs. 3, 4, 5, and 6) differs, in the 

 slightest degree imaginable, from that of the same part of the living 

 animal. I can merely discover that the great trochanter of the latter 

 is more pointed, and the slope separating it from the head is more 

 profound. I have one 0,6 in length, indicating a subject nearly thirteen 

 feet high, 



The Fossil Rotula is higher in proportion to its breadth than that of 

 the living animal, and more in the shape of a rhomboid. That in my 

 possession belonged to an animal seventeen feet and a half in length. 



The Fossil Tibia (plate 37, figs. 9, 10, 1 1, and 1 2) is thicker, in pro- 

 portion to its length, than that of the living animal ; which agrees With 

 the dimensions of the fore-arm, to give us to understand that the fossil 

 hippopotamus had shorter and thicker legs than the animal of our 

 times; but these differences in point of shape are very immaterial: 

 we can scarcely perceive that its inferior articulating surface is less 

 broad from. front to rear, and that its external condyle projects a little 

 more on the outside. Its length being 0,393, would indicate a subject 

 of twelve feet six inches ; but supposing the tibia to have been shorter 

 in proportion, we may allow a little more to the height of the animal. 



6. Bones of the Tarsus. 



The Astragalus (plate S2, figs. 1 and 4). — The fossil is the flatter of 

 the two; the ligamentous fossa of its pulley is much less hollowed, 

 and is smaller in proportion ; its great calcanean process is much 

 broader and of a quite different shape, proceeding to rejoin the tu- 

 berosity of the internal anterior angle of the inferior surface, from 

 which it is separated, in the living subject, by a wide fossa ; consequently 

 it is much broader in this particular spot, in the fossil. In every other 

 respect these bones bear a great resemblance to each other. 



The linear dimensions of the most perfect fossil astragalus which has 



