| | | | |Smooth. Faceted. | | | | | |4-tubercles, and crested | | | | | | |? Singly involute. | | | | | | | |Hemispheres small, and largeer. | | | | | | | | Eocene. Upper (Bridger.) |3-3, 4-3, 4-5 | |(Digitigrade.) Plantigrade. | | |Grooved. (Flat.) | | | |Opposite. Interlocking. | | | | |Smooth. | | | | | |4-tubercles. 3-tubercles, and crested. | | | | | | |Singly involute. Plane | | | | | | | |Hemispheres small. | | | | | | | | Middle. (Wasatch.) |4-3, 4-5, 5-5 | |Plantigrade. (Digitigrade.) | | |Flat. (Grooved.) | | | |Opposite. Interlocking. | | | | |Smooth. | | | | | |4-tubercles. 3-tubercles, a few crested. | | | | | | |Plane. Singly involute. | | | | | | | |Hemispheres small; | | | | | | | |mesencephalon sometimes exposed | | | | | | | | Lower (Puerco.) |5-5 | |Plantigrade. | | |Flat. | | | |Opposite. | | | | |Smooth. | | | | | |3-tubercles. (4-tubercles), none crested. | | | | | | |Plane. | | | | | | | |Mesencephalon exposed; | | | | | | | |hemisphere small and smoother. | | | | | | | | The evidence, then, which is furnished by all parts of the vertebral skeleton--whether we have regard to Fishes, Reptiles, Birds, or Mammals--is cumulative and consistent. Nowhere do we meet with any deviation or ambiguity, while everywhere we encounter similar proofs of continuous transformation--proofs which vary only with the varying amount of material which happens to be at our disposal, being most numerous and detailed in those cases where the greatest number of fossil forms has been preserved by the geological record. Here, therefore, we may leave the vertebral skeleton; and, having presented a sample of the evidence as yielded by horns and bones, I will conclude by glancing with similar brevity at the case of shells--which, as before remarked, constitute the only other sufficiently hard or permanent material to yield unbroken evidence touching the fossil ancestry of animals.