OSTEOLOGY OF THE AEMOKED DINOSAUBIA. 



Measurements of caudal spines No. 4937. 



Ill 





Anterior pair. 



Posterior pair. 



Right. 



Left. 



Right. 



Left. 





mm. 



mm. 

 623 

 275 

 170 



mm. 



370 



150 



80 



mm. 

 520 

 160 



so 





274 

 180 



Greatest extent transversely 



STEGOSAURTJS LONGISPINUS, new species. 



Type-specimen. — No. D54 Museum of 

 the University of Wyoming. Collected by 

 W. H. Reed and Prof. A. C. Dart in 1908. 



Type-locality. — About 1} miles east of 

 Alcova, Natrona County, Wyoming. 



Horizon. — Morrison Beds, Upper Ju- 

 rassic. 



The type-specimen consists of 42 verte- 

 brae from all parts of the backbone, frag- 

 mentary sacrum, two ischia, portion of one 

 pubis, right femur, several ribs and four 

 dermal tail spines, two of which are fairly 

 complete. 



Distinctive characters found in the der- 

 mal spines and posterior caudal vertebrae 

 make it necessary to create a new species, 

 and I therefore propose the name Stego- 

 saurus lonyispinus, the specific name being 

 suggested by the slender elongated nature 

 of the dermal tail spines. 



Detailed description. — The dermal spines 

 of S. longispinus are the longest so far 

 recorded. The most complete spine of the 

 four present measures 860 mm. in length 

 and the tip is missing. It is estimated that 

 the complete length of this bone would be 

 about 3 feet 3 inches (985 mm.). This spe- 

 cies is unique in the uniform development of 

 the basal portion of the spines, whereas in all 

 other described forms, where the spines are 

 known, the bases of the anterior pair greatly 

 exceed those of the posterior pair. This feature reaches its maximum development 

 in 8. sulcatus. 



The base of the spine shown in figure 66 has an antero-posteribr diameter of 

 145 mm. and a transverse diameter of 110 mm Like measurements of the other 

 three do not vary 5 mm. in either of these dimensions. 



Fig. 66.— Anterior pair of dermal tail spines of 

 Stegosaurus longisplnxis. Type. J) 54, University 

 of Wyoming collection. $ nat. see. (1) Lateral 

 view; (2) posterior view of same; (3) lateral 

 view of opposite spine, a, anterior border; p, 

 posterior border. 



