CLASS II CYSTOIDEA 185 
Hemicosmites, v. Buch. Calyx composed of four basal plates, two zones 
containing six and nine lateral plates respectively, and a circlet of six plates 
forming the ventral surface. The latter carries three short ambulacral 
grooves, at the ends of which are situated small articular facets for the 
attachment of arms. Rhomb-pores present on all of the side plates. Ordo- 
vician; Russia. HH. pyriformis, v. Buch. 
Caryocrinus, Say (Fig. 305). Calyx hexamerous, with dicyclic base. 
Infrabasals four, unequal ; followed by a second row (basals) of six plates, 
alternating with 
the plates of the 
first and third 
cycles. The latter 
ring consists of 
eight plates, six 
of which, accord- 
ing to Carpenter, 
represent the 
radials, and two 
(the interscapu- 
lars of Hall) the 
interradials. Ven- 
tral surface 

formed of six or Fic. po Fie. 306. 
5 Caryocrinus ornatus, Say. Silurian; Lockport, New York. ~ Echinoencrinus 
more small pleces. «a, Calyx from one side, with two arms attached ; b, Summit, striatus, v. Buch. 
natural size ; c, Inner and outer surfaces of calyx plate of the Ordovician ; St. 
All plates of the second circlet, with pore-rhombs. Petersburg. 
cup furnished 
with pore-rhombs; the summit plates imperforate. Mouth and ambulacral 
grooves subtegminal. Anus protected by valvular pyramid, and situated on 
the outer margin of the ventral surface. Here also are placed the arms, which 
are six to thirteen in number, and relatively feeble. Stem long, composed of 
cylindrical segments. Silurian; North America (New York and Tennessee). 
Echinoencrinus, v. Meyer (Sycocystites, v. Buch), (Fig. 306). Calyx com- 
posed of four basal plates, and three cycles containing five plates each. All 
calycine plates ornamented with costae or ridges radiating outward from the 
centre. Ventral surface with short ambulacral grooves, and articular facets 
for the attachment of three small arms. Anus removed to a lateral position 
between the first and second circlet of side plates. Three pore-rhombs 
present ; of these, two are situated above the base on the side opposite the 
anus, and the third above and slightly to the right of the anus. Stem round, 
short, tapering distally to a point, and composed of hollow segments inserted 
one within the other like the draws of a spy-glass. Ordovician; Russia. 
Glyptocystites, Billings. Ordovician ; Canada and Russia. 
Homocystites, Mimocystites, Barrande. Ordovician ; Bohemia. 
Family 7. Anomalocystidae. Woodward. 
—_—s—- Cally, more or less compressed, frequently with dissimilarly plated anterior and 
posterior sides. Plates either imperforate or with simple pores ; pore-rhombs absent or 
but few in number. Arms free; stem short, tapering distally to a point. Cambrian 
to Silurian. 
