CRINOID FROM THE SOUTHERN SEA. 
933 
being monocyclic only. It is curious, however, that Miller should make Glyptocrinus 
clecadactylus the type of a genus, the speciality of which is the presence of a mono- 
cyclic base. For Hall, Meek, and Wachsmuth* have all described it as being 
dicyclic, i.e., as possessing under-basals. 
It has been abundantly proved within the last few years that the presence or 
absence of under-basals upon the exterior of the calyx is a character which is generally 
of very little value for systematic purposes. Encrinus and Heterocrinus afford good 
instances of this. The late Mr. Meek, whose judgment Mr. Miller will hardly 
question, was fully aware of the great amount of variation in the cup of Heterocrinus , 
some species having one series of plates beneath the radials, and others, two; while lie 
further recognised that the upper row of the dicyclic base represents the single row of 
the monocyclic forms. 
The same is the case with Glyptocrinus and its allies, as was recognised by 
Wachsmuth and Springer, though Miller will not admit it. One would like to 
know whether he would rearrange the species of Heterocrinus on the principles which 
have led him to separate Gaurocrinus from Glyptocrinus. 
Description of the Figures. 
PLATE 71. 
The following lettering is used throughout all the figures :—cia, anal appendage; 
an, anambulacral plates; at, anal tube ; b, basals; b 2 , second brachial; c, cirrus ; cd, 
centroclorsal; i, interradial plates ; o, orals ; r, radials. 
Figs. 1-5. — Thaumatocrinus renovatus. All X 15. 
Figs. 1 and 2. Side views, radial. In 1, the right anterior, and in 2, the right posterior 
ray faces the observer. 
Figs. 3 and 4. Side views, interradial. Fig. 3 shows the left anterior interradius 
with its single large interradial (i) and anambulacral plates (an). 
Fig. 4 shows the posterior or anal interradius, in which the interradial plate bears 
the jointed anal appendage (act). 
Fig. 5. View of the disc from above, showing the anal tube and appendage, the oral 
pyramid, and the marginal zone of anambulacral plates. 
Fig. 6. Radial view of an Antedon- Pentacrinoid from S. 344, showing the lateral 
union of the radials. X 15. 
Fig. 7. Calyx of Thylacocrinus ; after Oehlert. 
Fig. 8. Anal side of Xenocrinus penicillus, showing the anal appendage (aa) ; after 
Miller. 
MDCCCLXXXIII. 
* Revision. II., p. 7. 
6 D 
