116 C. Wachsmuth—Structure of Paleozoie Crinoids. 
exception to the rule governing the class. It is true, the 
Ophiurans, for instance, have no separate anal opening, and the 
same aperture performs both oral and anal functions, but it is 
placed within the radial center and therefore cannot be homolo- 
gized with the interradial orifice of Paleozoic Crinoids. In 
Antedon rosaceus, although the nascent Crinoid develops 
already within the pseudembryo a separate mouth and_ vent, 
a single orifice serves for some time both as oral and anal aper- 
ture, yet it is the permanent mouth occupying the center of the 
ambulacral system.* While we thus find the mouth perform- 
ing permanently or temporarily anal functions, we have on the 
other hand no evidence either from recent nature or from em- 
bryology that an anus ever becomes developed into, or per- 
forms the office of, a mouth. ? 
The Crinoids of our present seas live exclusively on micro- 
scopic food, and we must expect to find that the Paleozoic Cri- 
noids subsisted upon very similar food and had a very similar 
mode of alimentation. enever in Aniedon alimentary par- 
wherein the furrows terminate. Dr. Carpenter remarks on this 
subject :+ ; 
“The transmission of alimentary particles along the ambula- 
cral furrows is the result of the action of cilia with which their 
transmission of minute apni along those portions of the 
immediately lead toward it; and 1t 
is, I feel satisfied, by the conjoint agency of these two mov- 
ing powers, that the alimentation of Antedon is ordinarily 
effected.” 
Ita rs from these observations, that the mouth of Ante- 
as 
nule, enters; a passage which might as well be external, hid- 
den beneath a vault, as open to the surrounding element, pro- 
* Sir Wyville Thomson, Phil. Trans. of the Royal Society. 
+ Researches on the Structure, Physiology and Development of Antedon rosa 
ceus. Part I, by W. B. Carpenter, M.D., F.R.S., Phil. Trans. Roy. Soc., vol. clvi, 
Part IL, 1866. 
