. Bulletin - United States National Museum. Science. 120 BULLETIN 89, UNITED STATES NATIONAL MUSEUM. type is shown in figure 71. There is not the sudden development of a rounded spine as shown in the scute described above. The edges fore and aft, from top to bottom, are sharp and the tiiangular spine is compressed transversely. Along the inner side of the base of both tliis and the preceding spme there is a longi- tudinal depression as if for its insertion in the sMn. Greatest height of this spme is 290 nmi.; greatest length antero-posteiiorly, 190 mm.; greatest width of base about 55 mm. (&am
. Bulletin - United States National Museum. Science. 120 BULLETIN 89, UNITED STATES NATIONAL MUSEUM. type is shown in figure 71. There is not the sudden development of a rounded spine as shown in the scute described above. The edges fore and aft, from top to bottom, are sharp and the tiiangular spine is compressed transversely. Along the inner side of the base of both tliis and the preceding spme there is a longi- tudinal depression as if for its insertion in the sMn. Greatest height of this spme is 290 nmi.; greatest length antero-posteiiorly, 190 mm.; greatest width of base about 55 mm. (&) Dermal elements with compi'eased grooved bases and spine; longitudinally grooved on posterior bordere. Throughout the entire length of the bone, a cross- section would be triangular in out- Ime, with the base resting on a level surface, the spine continuing upward, outward, and backward, overhanging the posterior border of the base (pl. 29, figs. 1 aud 2). The anterior or con- vex edge is sharp throughout its entire length. The body of the bone is mod- erately convex longitudinally on one side and correspondingly concave on the opposite side. In its general form it resembles most nearly dermal elements fomid with the skeleton of HylsRosaurus} The prmcipal features of tliis plate are well shown in plate 29. The greatest height is 330 mm.; greatest length antero-posteriorly, about 210 mm. (c) These have heavy, massive, expanded bases, spines compressed with edges, sharp both fore and aft; base somewhat obliquely beveled, spine curved outward; greatest height more than 270 mm.; greatest length antero-posteriorly, 175 mm.; greatest width of base, 150 mm. A modification of tliis type is sho^vn in plate 30, figures 1 and 2. The spinous part is reduced to a mere sharp ridge of bone rising from a massive base. It has the proportions of those placed by Nopcsa just in front of the pelvic shield in Polacanthti^ (fig. 72). Greatest height, 122 mm.; greatest length antero-posteriorly, 1
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