118 (r. R. Wieland—.Xotcx on the Armored Dinosquria. 



served plates of any specimen so far obtained. Indeed Brown,* 

 overlooking Polacanthus entirely, lias attempted with far less 

 material to restore the keels of his Anhylosaurus. But as 

 Willistonf has rightly said of this restoration, " It is based on 

 too scanty material to serve as a satisfactory basis for a restora- 

 tion * * since the form must be included in the. same family 

 as Polacanthus Hulke." "Whence it is pertinent to remark that 

 vertebrate paleontologists have reached the time when it is 

 well to realize that even though what is more a surmise or a 

 guess prove fortunate, its value both present and future must 

 depend on the concrete evidence which lies behind it, as we 

 have learned from severe experience. 



AVe may pass on to a brief notice of some further structures 

 of the mail-coated Dinosauria of much present interest. 



Pleural Armor of Stegosaurus. 



So far, the startlingly strange, complex,, and ornate aspect at 

 once indicated by even lesser portions of the mail-clad Dino- 

 saurs, has naturally led to so called "new families." Not to 

 mention a long series of genera of convenience, we thus have 

 the Scelidosauridse, Folacanthidse, Stegosauridee, Nodosauridee, 

 Ankylosauridfe, etc., etc. 



Now while this nomenclature of expediency may really 

 foreshadow the degree of complexity the mailed sanrians will 

 ultimately be found to exhibit, they are none the less to be 

 regarded as a compact and homogeneous series. And in all 

 likelihood this series displayed as much uniformity in the gen- 

 eral alignment of its keels as might be observed in a similar 

 array of Cretaceous Testudinate families. From our view- 

 point we hence hold it safe to predict that buttressing pleural 

 keels will certainly be found in addition to the two great and 

 firmly set dorsal Stegosaurian keels recovered. On both 

 anatomical grounds and relationship this must be the conclusion; 

 though it is very clear that such pleural keels would be loio, 

 since the mid-line armor had become the dominaut means of 

 defense, or at least region of accelerated growth. . Even so 

 there is in the nearly rigid back a most curious parallel to the 

 turtles, and we believe that restorations should take more cog- 

 nizance of this fact in dealing with the leg flexion than they 

 have so far. 



That pleural keels have not been so far recovered, or recog- 

 nized must be explained away as due to accidents of preserva- 

 tion and collection — even to paucity in field observations or 

 notes. At best the chance to find more or less loose peripheral 



* The Ankylosauridae, a new family of Armored Dinosaurs from the 

 Upper Cretaceous, by Barnum Brown. Bull. Am. Mus. Nat. Hist., vol. xxiv, 

 Feb. 13, 1908, pp. 187-201. 



f American Naturalist, vol. xlii, Sept., 1908, p. 629. 



