14 Von Buch on Crinoidea. 
and consequently of tentacula, is important. ‘They reappear 
on many Encrinites; for instance, on Actocrinites, on Rho- 
docrinites, and even on Marsupites. (Bronn, Lethza, Pl. IV.) 
The rhombs are not evident on the surface of Spheronites 
Pomum. Each plate bears a number of small systems, sepa- 
rated inter se. Two pores are always connected with one 
another, but these systems are scattered without arrangement 
over the entire surface. This species has hitherto only been 
found in Sweden. 
In the upper half of the Spheronites, but still a fourth of the 
sphere distant from the mouth, there is a large pentagonal 
aperture, which is closed by five triangular valves project- 
ing in a flattened pyramid. Gyllenhahl and his successors 
call this aperture the mouth. But analogy with the allied 
forms requires the mouth to be above, and an aperture closing 
exteriorly appears little adapted for a nutriment-receiving 
mouth. Probably it is an oviduct. Above, quite close to the 
mouth, and constantly to the right of the valvated aperture, 
there is a third very small opening, penetrating deep into the 
interior, probably an anus. A similar small anal aperture is 
likewise evident between three laminz on Apiocrinites, where 
hitherto it has not been observed, resembling the anus of the 
living Comatula. Gyllenhahl expressly states, “I always found 
this Spheronites Pomum in Westgothland, at a greater depth 
than Spheronites Aurantium, and in far greater number.” It 
is therefore surprising that it has not yet been met with in 
the neighbourhood of St. Petersburgh. : 
Hemicosmites pyriformis.—By means of this beautiful and 
extremely elegant form, we approach a great step nearer to 
the true Crinoidea. Although still without arms and closed, 
there are already here but few plates or assule, in definite num- 
ber and regularly combined. The Hemicosmites is reverse 
pear-shaped, and consists of three parts, of pelvis, thorax, and 
vertex. The pelvis on the slender pentagonal petiole is formed 
of four pieces, which are arranged in a hexagon. Two of them 
are pentagons, the two others lozenges (rhombs). Six costals 
in two different groups form the thorax. Three of these plates . 
are narrower, and above, between those on the left, there is 
a pentagonal aperture closed with valves as in Spheronites. 
The three other assulee are broader, and the superior apex of 
the elongated hexagon is somewhat truncated. In accordance 
with this, the vertical plates arching over the whole also 
divide into two groups; on the side of the broader assulz 
there is on each truncation of their apex a longitudinal piece, 
as it were, inserted, and there are therefore three such pieces ; 
they are wanting on the side of the valvate aperture. The 
exceedingly small laminz which cover the mouth on the top 
