Von Buch on Crinoidea. 15 
of the vertex, appear to terminate in three small processes or 
arms which are pierced, and might perhaps form distinct 
oval apertures. No anal aperture is evident. The great regu- 
larity of this arrangement is still more evident from the great 
elegance with which prominences are distributed in series 
over each assula of thorax and vertex. They proceed on the 
costals from the centre to the upper angle of the hexagon, 
none towards the lower. On the vertical assula, on the con- 
trary, these series go towards the lower angles, none towards 
the upper. Only the halves of the surfaces are decorated in 
this remarkable manner. The vertical and lateral series thus 
combine to form a highly elegant wreath environing the 
whole figure. These warts or prominences are pierced in 
the centre, and appear to be points of adhesion for spines. 
The central series of each assula is double. On the other 
parts of the assular surface there are but few similar warts 
scattered without any order. 
Cryptocrinites regularis and C. Cerasus (Pander, t. ii. 
f. 24. n. 26.). 
The pelvis is that of a Platycrinites, the thorax that of a 
Poteriocrinites; but the vertex is still closed, and without arms. 
However, five ribs or rings extending from the lower extre- 
mity to the vertex are hidden beneath the assulz, which are 
thus raised exactly in the form of a roof, just as may be 
observed in Actocrinites before the arms divide. The es- 
sential character of the Crinoidea exists, therefore, almost 
entirely in the Cryptocrinites, but it is yet hidden in the 
interior. The pelvis consists of three plates, which are 
united to form a pentagon, an arrangement which again 
occurs in Platycrinites, in Rhodocrinites, and in Actocpinites, 
but only in the older ones; in the later Jura Crinoidea 
it is no longer found. The thorax is surrounded by five 
costals, and the vertex likewise by five plates, which alter- 
nate with the costals. Minute plates surround the mouth, 
which is for the most part open. Between the vertex and 
costals there is again a large aperture covered by five valves. 
In Cryptocrinites Cerasus, intercostals are, moreover, situ- 
ated on the original five of the thorax, thus somewhat dis- 
turbing the regularity of the upper half; and there are also 
probably more than five assulze or plates on the vertex. The 
side on which the valvate aperture is situated is bulged out 
at all points; the effort of the hidden arms to break through 
the sides is here evident. The size of these animals sel- 
dom exceeds that of a pea; the petiole which bears it has 
the thickness of a pin. Hitherto they have occurred solely 
in the hills near St. Petersburgh. 
