Prof. O. C. Marsh—On Stegosaurus. 13 
The upper portion of the neck, back of the skull, was protected by 
plates, arranged in pairs on either side. These plates increased in 
size farther back, and thus the trunk was shielded from injury. 
a b c 
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Fic. 1.—Gular plate of Stegosaurus ungulatus, Marsh; a, superior view; 3, side 
view ; ¢, inferior view. 
From the pelvic region backward, a series of huge plates stood 
upright along the median line, gradually diminishing in size to about 
the middle of the tail. One of these is shown in Woodcut Fig. 3. 
a 
Fic. 2.—Caudal plate of same individual; a, side view; 4, end view of base ; 
c, view of opposite side; d, thin margin; ¢, rugose base; f, and f’, surface 
marked by vascular grooves. 
Some of the species, at least, had somewhat similar plates below the 
base of the tail, and one of these bones is represented in Woodcut 
Fig. 2. 
Fic. 3.—Dorsal plate of same individual; a, right side; 4, thick basal margin ; 
c, left side; other letters as in last figure. 
All the figures are one-twelfth natural size. 
The offensive weapons of this group were a series of huge spines 
arranged in pairs along the top of the distal portion of the tail, 
which was elongate and flexible, thus giving effective service to the 
spines, as in the genus Myliobatis. 
In Stegosaurus ungulatus, there were four pairs of these spines, 
diminishing in size backward. Two of the larger of these are 
