804 STUART WEELER 
flat across the central portion with the exception of a small 
_ square fractured area in the exact center. This fractured por- 
tion corresponds to a similar fractured area at the summit of the 
central prominence of the lower side, and really represents a 
perforation through the disk in its perfect condition. 
The impression of the upper side of the disk of another 
species is seenin Fig. 4, Plate A. The lobing of the periph- 
ery is different in this species, but its greatest peculiarity is in 
the presence of the impressions of four rather slender diverging 
spines, one on each quadrant, surrounding the fracture represent- 
ing the central perforation of the disk. 
In the limestone at Racine, associated with Cryptodiscus, the 
internal casts of some peculiar tubelike bodies have been found 
by Mr. Teller. Two views of the most perfect of these specti- 
menspare) Shown on later Eige 3.sand later a). ice /emmeeabe 
tubes are composed of plates arranged in ranges of four each, 
and in the specimen illustrated the impressions of three such 
ranges are preserved. The top range consists of two longer 
plates and two shorter ones; the middle range consists of two 
plates. below the shorter plates of the top range, which are placed 
higher than the two plates below the longer plates of the top. 
The lower ends of the basal range of plates are not preserved, 
but the summits are alternately higher and lower, to correspond 
with the plates of the middle range. 
The specimen which forms the connecting link between the 
disk and the tube 1s illustrated on) Elate sas wince: 25. lnsthis 
specimen the disk and the tube are both incomplete, but the 
relative position of the two is perfectly shown. The four quad- 
rants of the disk are shown to be but the greatly expanded 
margins of the four plates in the top range of the tube, and the 
central elevation seen in the impressions of the lower side of the 
disk, is the summit of the internal cast of the tube. 
When the relationship of the disk to the tube was recognized, 
the crinoidal character of Cryptodiscus could not be questioned ; 
and a comparison of the arrangement of the plates in the tube 
with the arrangement of the plates in the dome of Calli crinus, 
