270 
ON THE ECHINODEKMATA. 
forty-three genera, containing 176 species, are found, whilst in the 
Upper Silurian in North America there are sixty-two genera and 450 
species, so that in Europe we have a greater number of genera, but a 
smaller number of species, than are found in North America. The 
Lower Silurian forms are quite distinct from the species found in the 
Upper Silurian Rocks. The Devonian Rocks of England contain very 
few forms, whilst the Devonian Limestone of the Eifel, Nassau and 
the Hartz, Thuringia, Ardennes, Mayenne department France, Austria, 
Spain, and Russia contain many species, and the Devonian Rocks of 
North America are likewise rich in species, so that at the present time 
it is estimated that forty genera and 230 species are known from the 
Devonian formations of the Old and New Worlds. The carboniferous 
limestone contains an immense abundance of the plates and stems of 
Encrinites, so much so that this formation has been called the Encrinital 
Limestone. Bolland and Richmond in Yorkshire, Bakewell, Derbyshire, 
and Clifton, Gloucestershire, and the carboniferous limestone of 
Scotland and Ireland have yielded many remains. Germany and 
Belgium have added their contingent. North America has largely 
added to our knowledge of the Encrinital Limestone, and the five 
divisions into which the American geologists have divided their car¬ 
boniferous group, Kinderhook, Burlington, Keorur, St. Louis, and 
Chester groups, have yielded an immense addition to our European 
lists. In the Trias we are surprised to find so few Crinoids after the 
wonderful devolpment the genera and species attained in carboniferous 
times. The best known to us is the Encrinus moniliformis, of which I 
have a fine specimen in my hand from the Muschelkalk of Germany, 
and this figure will give you a good idea of its structure. When we 
compare this Crinoid with the forms from the carboniferous rocks we 
see at a glance the wide gap that separated the genera of these two 
formations from each other. The Jurassic Rocks contain an entirely 
new set of generic forms, the Pentacrinidce, of which the Pentacrinus 
basaltiformis is the best known. The specimens on the table and figures 
on the wall show us the beautiful form this genus assumed in the 
rocks beneath our feet. The stem is five sided, and in some species 
attains many feet in length, and is provided with a great number of 
side arms. It does not appear to have been attached by a thickened 
root to the bed of the sea, as was at one time thought to be the case, 
but to have attached itself by its side arms or the lower part of its 
stem into the mud, just as the Pennatula and Funiculina of our shores 
do now. Of the Pentacrinus, there are several living species which live 
in deep water. The Bristol Museums and the College of Surgeons, 
London, contain interesting examples from the Antilles. The Apio- 
crinidcB, with a pear-shaped cup, supported on a long round stem, 
which was firmly rooted to the bed of the sea, of which Apiocrinus 
Parkinsoni Bradford Pear Encrinite is the type. Upon the upper 
portion of the stem rests a broad centrodorsal plate, with five 
elevated radial borders, upon which the pieces of the radial arms are 
built, as you see in this figure and section of the fossil. 
