C. Wachsmuth—Structure of Paleozoie Crinoids. 128 
it, This is evidently the case. In a transverse section of 
the arm, with the help of a magnifier, I think I have detected 
within the tube, traces of two passages: a deep groove oceupy- 
lng only the median region, and on each side of it a smal canal, 
underlying the pores. The condition of the specimen does not 
enable me to say whether the two side passages connect at the 
ttom or not, but in either case, they undoubtedly represent 
the ambulacral canal, the food-groove occupying only the me- 
dian and upper part of the channel. 
It is to be regretted that in no instance the upper part of the 
tubular skeleton has been found in perfect preservation. re 
has been observed beneath the vault an annular vessel, con- 
structed of plates similar to those of the radiating tubes, with 
small openings directed toward the radial sides of the specimen, 
with the alimentary canal passing through the inner space o 
the ring, but its connection with the surrounding parts was 
not preserved. The position of the annular organ in the center 
of radiation leaves but little doubt that it is the cesophageal ring 
the to the direction of the tubes, indicates most strongly that 
the tubes and the circular organ were connected, and that the 
to the center, another series of passages, which passing the 
region of the annular vessel, unite in the center. I hold these 
2€ & continuation of the food-grooves in the arms, which 
evidently passing over the top of the circular organ termina 
within the central orifice. 
in all Echinoderms with an external mouth, is attached to the 
inner side of the test, is located in Paleozoic Crinoids at a 
distance from the vault. Howeve 
vault cannot be homologi with the oral skin of recent 
- Crinoids, and that only the tubular skeleton corresponds to the 
> , 
radiating passages connecting with the peristome, the vant 
