BARBADOS-ANTIGUA REPORTS 59 
In 1913 Springer and Clark’? placed Holopus, together with 
Cotyloderma (Cotylecrinus) and Cyathidium (Micropocrinus) 
in the family Holopide, the last (eighth) family of the order 
Articulata as understood by them. 
From a detailed study of the contrasting pairs of characters 
used in differentiating the recent crinoids Mr. A. H. Clark in 
1915 arrived at the conclusion that Holopus is in reality a 
highly specialized type, on a par with, or even possibly in ad- 
vance of, the pentacrinites and the comatulids, and much in 
advance of all the other recent forms. In 1919’? the same author 
expressed the opinion that, in spite of their extraordinary super- 
ficial dissimilarity, the pentacrinites, the comatulids and Holopus 
are very closely related. He says that in the pentacrinites the 
column is enormously developed; so rapid is the growth that 
the proximales as they are continuously formed beneath the 
ealyx never succeed in becoming attached to it, but are con- 
tinuously pushed outward by the formation of new proximales 
between the last formed and the calyx; the proximales later 
become separated by the intercalation of other columnals, ap- 
pearing in the fully developed column as the cirriferous nodals. 
The basals are much reduced and lie horizontally. In the coma- 
tulids a short column is formed and a proximale appears which, 
becoming firmly attached to the calyx, increases enormously in 
size, and, the larval column being discarded, contains the entire 
adult stem. The basals, in nearly all the types, become meta- 
morphosed into an internal septum and entirely lose their or- 
iginal character. The base therefore is entirely composed of 
radials, practically horizontal in position, plus the proximale. 
In Holopus the same line of specialization has apparently been 
followed further; the column and the basals have disappeared, 
and the attachment is by means of the radials, which in the 
comatulids dominated the base. It is conceivable that the very 
young Holopus is essentially like a short-stemmed comatulid in 
which the radials, growing very rapidly, form a cylindrical ring 
with the basals, spread outward until they all le in the same 
10In Zittel-Eastman, Text-book of Paleontology. 2nd Edition, p. 241. 
11 Phylogenetic study of the Recent Crinoids, Smiths. Misc. Coll., 65; 
no. 10 (Aug. 19, 1915). 
12 Jour. Washington Acad. Sci., IX (1919), p. 136. 
