TRANSFORMATIONS OF THE ECHINA, We 
sented. A highly remarkable and important interme- 
diate form is also known, found in the upper Silurian 
strata of Dudley (Eucladia Johnsoni), the more impor- 
tant as but few transitional forms between one order 
and another have been hitherto discovered. The rela- 
tion of the star-fish to the sea-urchins is still indistinct. 
On the other hand, the bridge from the stone-lilies to 
the sea-urchins is tolerably apparent. The true Crinoids 
are sessile, and with them are connected, in the carbon- 
iferous formation, the no longer sessile Cystoids and 
Blastoids, with which are associated the Tessellz, more 
resembling the sea-urchins. Now the Dyas and Trias 
are still poor in true Echine ; the Jura, on the contrary, 
very rich; and in this great period the extraordinarily 
heterogeneous transformations of the Echinz are slowly 
accomplished, and may be traced, step by step, from 
the Lias, the earliest oolitic formation, to the coral 
limestone. At first the Cidaridee predominate; they 
are joined in the Oolite by the Echinoconide and Cassi- 
dulidez. In the upper layers of the Jura, the sharper 
‘separation of the species becomes characteristic. 
Desor shows how this development, accompanied by 
temporary quiescence, is connected with the nature of the 
sea-bottom at the time. “ The law of progress,” he says, 
“is displayed in the circumstance that it is the lowest of 
the Echinz, the Regularze and Endocyclice, which pri- 
marily appear, first in the form of the Tesselle, then as 
Cidaride ; while the most perfect Spatange, with the 
most distinctly marked bilateral form, make their ap- 
pearance last of all. Between these extremes we find 
a host of genera and species distinguished from one 
another by mere shades, so that of two allied genera it is 
