. Bulletin - United States National Museum. Science. 92 UNITED STATES NATIONAL MUSEUM. Fig. 56.—Tubeeculak spine of Stego- SAUEUS UNGULATUS MAESH. y>j NAT. SIZE, a, SUPEEIOR VIEW; 6, INFEEIOR view; c, ENii VIEW. After Marsh. None of the isolated dermal structures figured by Marsh have been recognized with any National Museum specimen (fig. 56). Nuclial plates.—The plates borne upon the neck immediately posterior to the skull are small, thin, vertically elongated, with roughened basal ends, without material transverse expansion, except in very old individuals. In specimen No. 4934 there are
. Bulletin - United States National Museum. Science. 92 UNITED STATES NATIONAL MUSEUM. Fig. 56.—Tubeeculak spine of Stego- SAUEUS UNGULATUS MAESH. y>j NAT. SIZE, a, SUPEEIOR VIEW; 6, INFEEIOR view; c, ENii VIEW. After Marsh. None of the isolated dermal structures figured by Marsh have been recognized with any National Museum specimen (fig. 56). Nuclial plates.—The plates borne upon the neck immediately posterior to the skull are small, thin, vertically elongated, with roughened basal ends, without material transverse expansion, except in very old individuals. In specimen No. 4934 there are five of these small elongated plates as shown in plate 14. These gradually increase in height from front to back. As shown by No. 7615 (pi. 23, figs. 2 and 3), they are flat- tened on one side, probably the external, and slightly convex antero-posteriorly on the opposite side. The depth of the insertion of these plates in the skin appears to be indicated by an abrupt transverae constriction some 40 mm. above the basal end, well shown in figure 57, g. The character of the surface of this portion is also changed, inasmuch as the vascular grooves of the upper sur- faces end abruptly at the point of contraction. In other specimens this surface is roughened with fine interrupted ridges of bone, their general trend being antero- posteriorly. In some of the above plates there is a slight transverse bevehng of the lower end, and all agree in having one large foramen leading up into the ^ ^ interior of the bone. Dorsal plates.—The small elon- gated plates are succeeded by larger more or less oval plates, with trans- versely expanded bases, of very short fore and aft extent as compared mth the longitudinal diameter of the upper portion, apparently a provision for greater freedom of movement such as would be I'equired in the region of the shoulders (pi. 23,figs. 4, 5, and 6). In specimen No. 4934 there are four of these oval plates with bases cleft longitudinally. These increase rap
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