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, 

 140 mm.; greatest width of base, 100 mm. 



As may be readily seen from an inspection of the figures, these skin ossifications 

 in JIoplitosaunk<i present far more variety of form than do those obtained with the 

 remains of any American dinosaur Icnown at the present time. 



They vary all the way from small, rounded tubercles to plates of good size, and 

 from simple flattened scutes to those with sharp ridgings and sjjines. 



Fig. 71. — Dermal plate of Hoplttosadrus makshi (LncAS). 

 Type. No. 4752, U.S.N.M. } NAT. size. 1, Lateral tiew; 2, 



END YIZV,' OF SAME. 



' See d.d.d. pl. 4. Fossil Reptilia of the Wealden and Purbeck, 1858, p. 25. 



