THE DINOSAURS 107 
ran series of large, but thin, and sharp-edged 
plates standing on edge, so that their backs 
looked like the bottom of a boat provided with 
a number of little centreboards. Just how 
these plates were arranged is not decided be- 
yond a peradventure, but while originally fig- 
ured as having them in a single series down 
the back it seems much more probable that 
they formed parallel rows. 
The largest of these plates were two feet in 
height and length, and not more than an inch 
thick, except at the base, where they were en- 
larged and roughened to give a firm hold to 
the thick skin in which they were imbedded. 
Be it remembered, too, that these plates and 
spines were doubtless covered with horn, so 
that they were even longer in life than as we 
now see them. The tail spines varied in length, 
according to the species, from eight or nine 
inches to nearly three feet, and some of them 
have a diameter of six inches at the base. 
They were swung by a tail eight to ten feet 
long, and as a visitor was heard to remark, one 
wouldn’t like to be about such an animal in 
fly time. 
