370 «=F. B. Meek—Fossils of the Illinois Geological Report. 
the text, I have thought it desirable to indicate here more fully 
the particular figures on this plate, to which the student should 
refer while reading certain paragraphs of the remarks mentioned. 
For instance, in connection with what is there said in regard 
to the structure of Cyathocrinites on pages 825 and 326, figures 
13 and 14 of plate 1x should be consulted. Figure 14 rep- 
resents the upper side of Cyathocrinites malvaceus, as seen with 
the ventral tube and some other parts removed. In this con- 
dition, there would, on a hasty examination, seem to be two 
principal openings above, directly into the visceral cavity. 
That is, the posterior one (an), at the lower part of the figure, 
for the connection of the ventral tube, and a large central one 
opening (seen at A in fig. 14) were through these covered am- 
bulacral canals (ame of fig. 18), and under the small central 
vault-pieces covering the central opening itself* ie 
The discovery of this structure of the vault of Cyathoerinules 
is one of considerable interest, since it brings to light one ot the 
most marked distinctions between this genus and Poterioermiles 
(including as subgenera Scaphiocrinus, Zeacrinus, Homocrinus, 
&e in which no such vault-structure exists, the whole 
acri- 
even questioned the propriety of viewing them as distinct 
* The form and size of these central yault-pieces may not be exactly as repre 
sented in fig. 13, as the sutures there are very obscure in the specimen, and they 
are too strongly and decidedly defined in the engraving. 
. 4 
