Figure 2.—Pelvis of "Atlantosaurus immanis" Marsh; seen from the left, one- twentieth natural size. The signification of the letters is the same in both figures, viz: a, acetabulum ; f. foramen in pubis ; il. ilium; is. ischium; p. pubis; p', post-pubis. In these and the following diagrams of Dinpsaurian pelves, the three bones of each are represented nearly in the same plane.