OSTEOLOGY OF THE ARMOBED DINOSATJKIA. 



119 



(5) Of the spined scutes there are portions of eight present, five of which are 

 nearly perfect. The form of all when viewed laterally may be roughly described 

 as triangular, and nearly all are elongated and asymetrical. For convenience of 

 description these may be subdivided into the following: 



(a) Scutes with median, transversely expanded, oblique bases; above base 

 greatly expanded antero-posteriorly, contracting rapidly to a rounded spine which 

 rises from near the center of the plate, tapering to blunt upper extremity. What 

 I take to be the external side is angularly convex antero-posteriorly, the inner 



Fig. 70. — Deemal scutes of Hoplttosaurus marshi (Lucas). Type. Cat. no. 4752, U.S.N.M. i nat. size, a. Ridged 

 scute; a', cross-section of same; &, triangular scute; 6', cross-section of same; c, circular ridged scute; c' cross- 

 section of same; d, circular noded scute; d' , cross-section of same; n, node-like elevation. 



side being less so. The anterior and posterior edges of the lower third of the plate 

 present sharp borders, becoming more obtuse as they pass into the spine. Cor- 

 recting the measurements given by Lucas of the spine shown in plate 28, the 

 greatest length is over 390 mm. ; and the greatest length antero-posteriorly is 280 

 mm. If ISTopcsa is correct in the placing of the dermal armor in the restoration 

 of the English Polacanihus, these spines would pertain to the anterior half of the 

 animal, as shown by the close resemblance of the present spines as compared with 

 those of that genus. (Compare pi. 28 with fig. 72.) Lucas in his description 

 considered them as belonging to the distal caudal region. A modification of this 



