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120 C. Wachsmuth—Structure of Paleozoic Crinoids. 
in all Crinoids. at we find no trace of it in some of the 
casts is no.proof to the contrary; it may have been sometimes 
composed of more perishable material and was not preserved, 
or situated at a greater distance from the vault and covered by 
the substance of which the casts were formed. 
2. The ventral furrow of the arms, 
The arms of Paleozoic Crinoids manifest great diversity 
in outer form and structure, but are invariably provided with 
a ventral furrow, which continues from the arm bases up to 
the tips of the arms and along the pinnule. The pinnule 
spring out alternately right and left from the arm-plates, their 
urrows connecting with that of the arm and forming in fact a 
continuation of the same : 
he furrow appears, in specimens in ordinary preservation, 
: : pain 
tained. The best specimen of this kind, that I have seen, is 4 
Cyathocrinus malvaceus, in which the little plates above the fur- 
row can be studied in all their details, with the greatest pre- 
‘cision. The specimen is the property of Frank Springer, Esq., 
who had the kindness to leave it with me for investigation and 
description. The arms of Cyathocrinus are composed of long 
slender joints with a wide ventral furrow. They bifurcate fre- 
quently, each branch bifurcating at intervals again. There 
appears on the arms of Cyathocrinus no scar for the attachment 
of pinnule, and as these appendages have never been observed 
in the genus, it is probable that the many little branches per- 
formed their functions. In Mr. Springer’s specimen the plates 
above the furrow consist of two rows of minute pieces, on 
