: 
: 
r 
z 
; 
% 
‘ 
z 
. 
ON COLLECTING FOSSIL ECHINODERMATA. 331 
Carboniferous formation. The most ancient Echinide, ac- 
cording to the present state of our knowledge, are the Cidares, 
in the modified form previously noticed,—<Archeocidaride 
(ante, p. 322). 
In the Trias another type appears, Hemicidaris, which 
holds an intermediate place between the Cidarites properly 
so called and the Diadema. 
In the Oolite, and Jurassic formations, numerous forms are 
for the first time met with, constituting the genera Echinus, 
Clypeus, Disaster, Holectypus, Diadema, Nucleolites, &c. 
The Cretaceous seas swarmed with echini belonging to 
genera of which no traces have been found in earlier rocks; 
viz. Holaster, Salenia, Micraster, Salerites, Discoidea, Anan- 
chytes, Cassidulus, &c. 
In the Tertiary formations, Spatangus, Scutella, Clypeas- 
ter, and other new genera appear, and many of the ancient 
ones are absent; or at least have not been observed. Of 
the genera printed above in italics, no living species are 
known. 
ON COLLECTING AND DEVELOPING FOSSIL ECHINODERMATA.— 
In the previous remarks on the fossil remains of radiated 
animals, we have pointed out those remains that are the 
most important and instructive, and should be sought for 
by the student. Thus, in collecting Crinoids, the receptacle 
or body should be the principal object of research, and if 
only detached plates can be extracted from the rock, their 
relative position should be carefully noted, and the specimens 
glued to a card or board, in their natural order; and some 
of the ossicula of the column, and of the arms, or tentacula, 
be placed with them. 
Mr. Miller dissected specimens of every genus, and has 
figured the separate plates or bones that enter into the com- 
position of the receptacle,* and arms. Traces of the ten- 
* Natural History of the Crinoidea. 
