CRINOID FROM THE SOUTHERN SEA. 
929 
is perfectly true, and the distinction sharply marks off the section of bilateral 
Glyptasterites from the pentahedral Rhodocrimtes. 
The section Glyptocrinites, however, is somewhat heterogeneous. Its calyx is said 
to be almost perfectly pentahedral with the “ interradial areas depressed, the first 
plate resting either directly upon the basals, or between the second and third radials, 
without special anal plate beneath their line.” Only three genera are included in 
this section, and Messrs. Wachsmuth and Springes, seem to have been somewhat 
uncertain about so grouping them; for they remark (p. 183), “It might have been 
not out of the way if we had placed the genus Glyptocrinus in a group by itself, as it 
differs from Archceocrinus and Reteocrimis, with which it has been associated, arid 
from all other Rhodocrinidcef in having the first plate at each interradial side placed 
between the second radials.” 
In Archceocrinus (W. and S.), on the other hand, the lowest interradials rest 
directly upon the basals, as is also the case with the small and irregular interradials 
of Reteocrinus. Both these genera, therefore, have isolated radials and a pentahedral 
symmetry (“somewhat bilateral” in Reteocrinus) just as in the Rliodocriniles. But 
the latter lack the “ rounded strongly elevated ridges ” which distinguish the radials 
of Archceocrinus and Reteocrinus. This, however, is merely a character in the 
superficial ornamentation of the calyx; and it seems to me of altogether minor 
importance as compared with the morphological differences between the lateral union 
and the isolation of the radials. In this last feature Archceocrinus and Reteocrinus 
resemble the Rhodocrimtes, and if the limits of that section could not be enlarged to 
receive them, they might very well be left in a group by themselves, distinguished by 
their ornamentation. 
But they are out of place by the side of Glyptocrinus, with all its radials united 
laterally. It thus represents a comparatively late ontogenetic condition, not even the 
radials of the posterior side being separated by an anal plate as in the Glyptasterites. 
There are,doubtless,close affinities and remarkable transition forms between Glyptocrinus 
and Reteocrinus, as asserted by Messrs. Wachsmuth and Springer. But these 
depend very largely upon the characters of the rays and arms, which are of a 
comparatively subordinate value ; while the lateral separation of the radials in the 
last named genus, and in the Rhodocrimtes , is a fact of considerable importance in 
Crinoid Morphology. 
It must be remembered also that Glyptocrinus has decided affinities with some of 
the earlier Actinocrinidce, certain species appearing to be without under-basals. In 
fact, according to the American authors, “ It is a question whether that genus, at 
least partly, should not be arranged with the other group altogether.” 
Thus, then, I would divide the Rhodocrinidce (W. and S.) into groups as follows :— 
* The italics are mine. 
