E. Billings on the structure of Crinoidea, Cystidea, ete. 289 
In ae. 13, Ngati — _ the cant ied the 
mallest specimen of ‘Caryocrinu vatus, 
in our co Menton selected for he Scena 
. _ «) purpose because in the young of this spe- 
"@: ®, / cies, the valvular orifice is larger in pro- 
ere portion to the size of the dise, than it is in 
the adult. It is in this specimen, about 
one-third of the whole width of the apical disc, while in a full 
grown Caryocrinus it is only one-ninth of the width. The 
same proportional size of the mouth according to age, occurs in 
o ° bd 
Sensi t Lwael say that they were 
According to the new theory, this Pe ehee es tae 
ornatus was a polystome animal, and drew in its food es : 
its six ovarian hep abes the large valvular one being the 
anus. ‘To me this appears to be utterly incredi 
In fig. 14 I have Te peceaien the mouth of Jeakea mirabilis 
Gray. Both Dr. lL E. Gray and Prof. Lovén have pronounced 
this aperture to have the structure of the valvular orifice of the 
Cystidea. I have not the slightest doubt wer es but that the 
mouth of the Cystideans foreshadows that hi 
There is nothing whatever in its structure iy Sac that it is not 
the mouth but on the contrary. 
The new theory is not founded upon any peculiarities in the 
structure of the ambulacral orifices, bear would show that 
they are oral apertures, but only u the four papeeions 
above noticed. The first of these is BoE logical, while at the 
same time it is Bie fa theoretical, and avai ates against 
i 
stance, i. e., according to the second the supply of water to the 
