THE OLD RED SANDSTONE. 43 
mounted on the paddles of the whale, why not find in the 
Old Red Sandstone the body of the tortoise mounted in a 
somewhat similar manner? ‘The idea originated in error ; 
but as it was an error which not many naturalists could have 
corrected at the time, it may be deemed an excusable one, : 
more especially by such of my readers as may have seen 
well-preserved specimens of the creature, or who examine 
the subjoined prints. (Nos. I. and II.) I submitted some of 
my specimens to Mr. Murchison, at a time when that gentle- 
man was engaged among the fossils of the Silurian System, 
and employed on his great work, which has so largely serves 
to extend geological knowledge regarding those earlier peri- 
ods in which animal life first began. He was much inter- 
ested in the discovery: it furnished the geologist with addi- 
tional data by which to regulate and construct his calculations, 
and added a new and very singular link to the chain of 
existence in its relation to human knowledge. Deferring to 
Agassiz, as the highest authority, he yet anticipated the de- 
cision of that naturalist regarding it, in almost every particu- 
lar. I had inquired, under the influence of my first impres- 
sion, whether it might not be considered as a sort of interme- 
diate existence between the fish and the chelonian. He 
stated, in reply, that he could not deem it referrible to any 
family of reptiles; that, if not a fish, it approached more 
closely to the crustacea than to any other class; and that he 
had little doubt Agassiz would pronounce it to be an 
ichthyolite of that ancient order to which the Cephalaspis 
belongs, and which seems to have formed a connecting link 
between crustacea and fishes.* The specimens submitted to 
* The aborigines of South America deemed it wonderful that the 
Europeans who first visited them should, without previous concert, 
