. Bulletin - United States National Museum. Science. OSTEOLOGY OF THE ABMOKED DINOSAXJKIA. 97 arrangement of the plates is shown and the original idea of four pairs of spines retained. The type of Stegosaurus stenops (No. 4934) corroborates most conclusively Lucas's interpretation of the arrangement of the dorsal armor, and, except in one or two points, I would indorse his restoration (pi. 34, lower figure) as being in accord mth the evidence shown by the specimens in the United States National Museum collections. The reasons given by I^ucas for the alternating position, as stated in an unpub-
. Bulletin - United States National Museum. Science. OSTEOLOGY OF THE ABMOKED DINOSAXJKIA. 97 arrangement of the plates is shown and the original idea of four pairs of spines retained. The type of Stegosaurus stenops (No. 4934) corroborates most conclusively Lucas's interpretation of the arrangement of the dorsal armor, and, except in one or two points, I would indorse his restoration (pi. 34, lower figure) as being in accord mth the evidence shown by the specimens in the United States National Museum collections. The reasons given by I^ucas for the alternating position, as stated in an unpub- lished manuscript, were twofold: First, that the plates did alternate as they lay embedded in the rock, and, second, that no two of them were precisely similar in shape or dimensions. Opposed to this argument. Lull has advanced the opinion â ' that the position of the plates in the rock is hardly conclusive, for the series might easily have shifted forward or backward slightly during maceration or in the sub- sequent movement of the ; A careful study of this series of plates leads to the belief that such a shifting has not taken place. For example, part of this series, as shown in plates 2, 4, and 14, has fallen to the left and lies under the body of the animal, while the posterior plates are approxi- mately in position above the pelvic region, yet both sections show the same alternating arrangement. Moreover, there is a remarkable mriformity of the overlapping of plates of one side upon those of the opjDosite rowâthat is, the middle point of the underlying plates, taken longitudinally, is, in neaiiy all instances, in the center of the interspace between the plates of the uppermost sei-ies (pi. 14). This exact spacing of the plates would indicate that they remamed attached to the skin imtil becoming fixed in the position in which we now see them. If this be true, it is difficult to explain the possibifity of bringing the plates of opposite sides into afignment, sin
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