Siluric Cystoidea and Camarocrinus. — Schuchert. 235 
Basal row has plates 4, 1, 2, 3. 
Second row has plates 10, 5, 6, 12, 7, 8, 14, 9. 
Third row has plates 16, II, 17, 18, 13, 19, 15. 
Fourth row has deltoids 20, 21, 22, 23, 24. 
Anal area bounded by plates 7, 8 and 13. 
Pectinirhombs normally situated, small, discreet, and with 
but few dichopores. 
As all the specimens are internal casts of the theca, the na- 
ture of the ambulacra, anal area, sculpture and column can- 
not be given. 
Genotype, Hcmicosmites subglobosus Hall. 
The above definition shows that Coelocystis differs widely 
from Sphaerocystites in that it has 6 additional plates and that 
these have quite another arrangement. The second row of the 
former genus has all the plates of the latter and in addition 
plates 10, 12, and 14 ; the third row has 7 plates and takes in all 
the plates of the fourth row in Sphaerocystites while the del- 
toids of the fourth row in Coelocystis, 5 in number, are not 
present (except 21) in Sphaerocystites. 
A comparison of the definitions here given with that of 
Sphaerocystites Jaekel (not Hall) shows that the latter omits 
plate 10 in the second row and has 6 plates in the fourth row 
against 5 seen in three examples in the National Museum. 
Both definitions, however, have 24 plates, but these are some- 
what differently arranged. The writer's material is excellent 
and while there is considerable difference in the shape of the 
plates in different specimens, yet there seems to be no error in 
the interpretation of their arrangement here given. 
Pseudocrinites gordoni n. sp. 
Length of the largest theca 32 mm., greatest width 32 mm., 
depth 21 mm. 
Ambulacra angularly elevated, prominent, extending around 
the entire periphery of the theca, and touching the column in 
specimens 20 mm. or more in length. In some of these mature 
specimens the ambulacra when near the column are deflected 
and one or both will pass on the same side for a short distance 
in front of it. In smaller specimens the ambulacra do not quite 
attain the column and in one having a thecal length of 15 mm. 
they stop within 3 mm. of the stalk. In the largest specimen 
there are 40 brachioles on each side of an ambulacrum while in 
