444 CLASS ECHINODERMATA. 
various heights. In the centre of the radii is the mouth, and 
the anus on one side. 
There is in the seas of Europe but one very small species, 
Pentacrinus Europeus, Thomson, Monogr., which is attached 
to divers lithophytes. 
The seas of the warmer climates produce larger and more 
complex species, such as Hncr. asterias, Blum., Isis aster., 
Linn. 
But the fossil encrini are very numerous, and vary suffi- 
ciently in detail to be divided into several subgenera, ac- 
cording to the composition of the central body, placed at 
the summit of the stem, and from which the large radii 
proceed. 
This body may be formed of pieces articulated with the 
stem, and supporting radii by similar articulations. Then if 
the stem is round and enlarged at the top, these are the 
APIOCRINITES, Mill. 
If it is round, but not enlarged, the ENCRINITES, 
If it is pentagonal, the PENTACRINITES. 
Or this body may be formed of angular laminz, joined 
together by their edges, and forming several ranges. 
Among those 5 
The PLATYCRINITES have but two ranges, one of three 
lamine, the others of five. 
The POTERIOCRINITES have three ranges, each of five 
plates. 
The CYATHOCRINITES have also three, each of five, but 
the last has some intercalary laminz, which may increase it 
even up to ten. 
The ACTINOCRINITES have several ranges, the first of 
three, the second of five, the others more numerous. The 
first two have radiated crests. 
The RHopocrINITES have also several ranges, the first 
