124 BULLETIN 89, UNITED STATES NATIONAL MUSEUM. 



lower figure, and 35, upper figure) and a general rearrangement of the plates of 

 the dermal armor. The alternation of the plates of opposite rows is shown, but 

 the median part of the tail was bereft of its dermal adornment. The reason for 

 the latter change is difficult to conjecture unless it were reasoned that it allowed 

 greater freedom of movement and thus facihtated the use of the tail as an offen- 

 sive instrument so that the dermal spines near the tip could be brought into action. 

 At best it is more fantastic than in accord with the known facts. 



The latest conception (pi. 36, lower figure), as exemplified by a recently mounted 

 skeleton 1 in the Peabody Museum of Yale University, erected under the direction 

 of Prof. P. S. Lull, and after which he has prepared a small model 2 (pi. 36, upper 

 figure) of the animal as he appeared in the flesh, shows a return to the paired arrange- 

 ment of the plates and the retention of four pairs of spines on the tail. 



Since the mounted skeleton and life restoration by Lull embody all of the latest 

 ideas (up to the year 1912) regarding the articulation of the bones of the skeleton 

 and the life appearance of Stegosaurus, it only becomes necessary for me to point 

 out wherein they differ from the facts revealed during this more recent study of a 

 large series of Stegosaurian remains. I appreciate only too well the difficulties 

 encountered in mounting for the first time the skeleton of one of these huge and 

 grotesque creatures, and in justice to Professor Lull I would say that he now recog- 

 nizes the correctness of some of the observations recorded below. 



It is in the dermal armor that the greatest alterations are now to be made, 

 and since the evidence for these changes is discussed in detail in the descriptive 

 part of this paper, it is only necessary to enumerate them here. 



1. The plates of opposite rows alternate, not paired as shown in the restoration. 



2. There are not more than 22, and perhaps only 20, in the complete series of 

 flat plates, whereas the restored skeleton shows 2S. It is quite possible, however, 

 that the number of these plates may vary, within limits, with the individual. 



3. The largest plate of the series, as shown by the two individuals found in 

 situ, is above the base of the tail, not over the sacrum. 



4. Dermal spines number four, based on the evidence of association in six 

 individuals. 



5. Number of overhanging spine-like caudal plates to be reduced from six to 

 two, on the evidence of two individuals. 



6. First plate of the series above the atlas, not over the fourth cervical, as 

 shown in the mounted skeleton. It is of interest to note that Owen figures the first 

 pair of dermal elements in Scelidosaurus (as found in the matrix) immediately 

 above the atlas. 



7. Bases of the plates of opposite rows throughout the series, comparatively 

 close together on either side of the middle line of the back. Not supported by the 

 upwardly directed transverse processes of the dorsals. 



8. Although the evidence is not conclusive, there is every probability that the 

 small rounded, so-called gular ossicles covered the top and sides of the head and 

 neck, rather than the throat, as represented in restorations (pi. 32, upper figure). 



' Amer. Journ. Sci., vol. 30, 1910, figs. 2, 3, and 4. - Idem, pi. 2, and fig. 10. 



