Nodosaurus textilis Marsh. 119 



certain portions of the body, as over the ribs, the one 

 series in part overlay the other. Wliat they really repre- 

 sent was suggested by Wieland (1911, 1912), although 

 not for Nodosaurus specifically. They are ossifications 

 of the two — the outer and the nether — dermogene layers, 

 the larger nodular plates being derived from the outer 

 and the lesser from the nether. Wiedersheim (1907, p. 

 25) states: 



'^In the derm [of reptiles], a superficial and a deeper layer 

 may be distin^iished. The latter is composed mainly of strong 

 bundles of connective tissue fibres which as a rule cross one 

 another at right angles, as in fishes and amphibians. ' ' 



This would account for the textile character of the 

 smaller subdermal (nether-layer) ossicles which are 

 merely ossifications or calcifications of this fibrillar 

 connective tissue. Marsh's statement that the interwoven 

 striae are on the external surface is true, but they are 

 just as visible on the internal surface and there is reason 

 to believe that in the figured specimen the inner and not 

 the outer aspect is exposed, as armor plates of the dermal 

 (outer dermogene) layer lie contiguous to the surface 

 which is embedded in the matrix. Another fragment 

 shows the relative position of the two armor layers very 

 clearly. The ossicles of the subdermal layer average 

 some 16 mm. square, though varying in length. Their 

 thickness averages about 3 mm. (see fig. 1). 



Dorsal armor. — One mass of matrix contains a group 

 of fiYQ or six ribs (pi. 1, fig. 3) overlain in part by the 

 armor. The ribs themselves have shifted somewhat from 

 their position during life, so that at least three of them 

 converge distally {r, r). These three are mainly matrix 

 impressions, with very little actual bone remaining, and 

 here the armor is lacking. The other ribs are covered 

 with the typical nodular armor of the outer dermal layer, 

 and here again two sorts of scutes are discernible, for 

 the larger nodular scutes are intercostal {icp) in position 

 as preserved and are separated one row from another 

 by a series of smaller rectangular scutes {cp), the surface 

 of which is approximately plane except for the rugosity 

 of the entire outer dermal series. The rows of smaller 

 rectangular scutes are costal in that they approximately 

 overlie the broadened outer surface of the ribs, although 

 sometimes shifted slightly post mortem. The smaller 

 scutes average 25x28 mm. in size. They are not every- 

 where distinct, but were probably pretty regularly dis- 



