Pia Seat Siac 60 a, 
Ae Feel ae 
APPENDIX. 
Arr. XTX.—Principal Characters of American Jurassic Dino- 
saurs; by O.C. MarsH. Part IV. Spinal Cord, Pelvis, and 
Limbs of Stegosaurus. With three Plates. 
_ Iva previous article,* the writer brought together the more 
Important facts then known in regard to the Stegosauria, one of 
the most singular groups of extinct reptiles hitherto discovered. 
n the present communication some additional characters of 
these animals are recorded, even more remarkable than those 
previously brought to light. 
Tue Brain anp Sprnat Corp. 
The general form and comparative size of the brain in this 
reptile is represented in Plate VI, figures 1 and 2. 
During a subsequent investigation of another individual of 
the same genus, the writer found a very large chamber in the 
sacrum, formed by an enlargement of the spinal canal. This 
chamber was ovate in form, and strongly resembled the brain 
case In the skull, although very much larger, being at least ten 
times the size of the cavity which contained the brain. This 
remarkable feature led to the examination of the sacra of sev- 
eral other individuals of Stegosaurus, and it was found that all 
5 a similar large chamber in the same position. The form 
* This Journal, vol. xix, p. 253, March, 1880. 
lla 
