592 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXIII. 



Another plate, probably from the dorsal series, is much more com- 

 pressed than either of the two alread}' noted, and seen in profile has 

 the form of a rather narrow, high triangle. 



None of the large, thin, flattened plates, so characteristic of Stego- 

 saurs hitherto described, are present, and while the material available 

 is too scanty to warrant any positive assertion regarding them, yet it 

 seems probable that in the species under consideration all the plates 

 were small and heavy. 



The nuchal armor consists of small, thick, irregularly quadrilateral 

 plates, slightly keeled, and these, save for their smoothness, are sug- 

 gestive of the nuchal and dorsal plates of crocodiles. 



The throat was protected by rounded ossicles varying from 3 to 25 

 mm. in diameter, and man}?^ of these are present on the slab containing 

 the nuchal plates. It is entirely probable that this species represents 

 a distinct genus of Stegosaurs; but in the absence of material on which 

 to base a generic diagnosis it seems best not to bestow upon it a new 

 generic name. 



This specimen Avas recognized by the late Prof. O. C. Marsh as repre- 

 senting a new form and, as it was almost the last specimen to be studied 

 by him, it seems particularly appropriate to name the species in honor 

 of one who did so much to make the Stegosaurs known. 



The following are the measurements of the spine and plates described: 

 Caudal spine, shown on Plate XXIII, 370 mm. high and 252 in antero- 

 posterior diameter; caudal plate, shown on Plate XXIV, 304 mm. high 

 and 155 in antero-posterior diameter; width of articular face 148 mm. ; 

 dor.sal plate 380 mm. in greatest height, and 198 in antero-posterior 

 diameter. 



