E. Billings on the structure of Crinoidea, Cystidea, etc. 229 
of Pentremites, belong to the Rus system of Professor 
Wyville Thompson; that it is doubtful whether or not the 
lancet plates oa Patel a with the radial plates of the Cri- 
noids; and t he ambulacra are more complicated in their 
structure ‘hick is ville supposed. 
7. . the Structure : the genus Nucleocrinus. 
5. 
ig. 3.—Apex of Nucleocrinus Verneuilii Troost. g, ambulacral groove; p, pore 
through which groove — se the interior ; s, one of the ten spiracles; mu, : 
oro-anal aperture. 4. prod of a specimen; a, the anterior in terradial. 
- Apex ~ a — etek ant ele  intoxzument that covered the center. 
e plates of the epee te the basals; c, 
plates of ‘the apex ; ¥ one of the “et anne 3 forked plate 
ether pon sintp to 
sabe the icipated basal plates of Pashenttis They 
presented at fig 6, 5, as figured by Mr. Lyon (Geol. Ky” col 
ii ny v, fig 1, 6.) 
