58 IOWA STUDIES IN NATURAL HISTORY 
difference between the excessively delicate epithelial layer lining 
the wall of the genital canal and the well developed cellular 
lining of the celiac and subtentacular canals is much less 
marked than in other types. The genital cord is of essentially 
the same nature as in the other ecrinoids, though it is of a much 
less branching character in the axillary than is usually the ease 
so near the dise. It is connected with ovaries alternately on 
opposite sides of the arm from about the first to the fifteenth 
brachial. The ovaries are short and stout, and confined to the 
pinnule bases in the broader lower parts of the arms; but where 
the segments are smaller the ovaries appear immediately be- 
neath the water vessel, and the boundaries between the three 
arm canals cannot be traced. The ova, of which all stages are 
visible, are more like those of Heliometra glacialis than is the 
case in many comatulids, but they are somewhat larger, reach- 
ing a diameter of 0.22 mm., while 0.1737 mm. is the size of the 
largest ovum of Heliometra glacialis which was measured by 
Ludwig. 
Carpenter remarks that all the specimens of Holopus which 
have been preserved in the dry state are of a dull dark green 
tint, sometimes verging on black; but Mr. Agassiz records that 
on one oceasion, off Montserrat, the ‘‘Blake’’ dredged an im- 
perfect whitish specimen. 
Carpenter treated one of the dry specimens of Holopus with 
aleohol and obtained a dull green solution with a red fluores- 
cence. Professor Moseley examined this with the spectroscope, 
and found the coloring matter to be identical with the penta- 
erinin which he had discovered in the pentacrinites dredged by 
the ‘‘Challenger’’ in the Pacific and in the East Indian archi- 
pelago. 
Carpenter discussed at considerable length the systematic 
position and relationships of Holopus; he associated with it in 
the family Holopide the genera Eudesicrinus, Cyathidium and 
Cotylecrinus. 
In 1891 Jaekel® in a paper ‘‘Ueber Holopocriniden’’ discussed 
the genus Holopus, associating with it in the same family Holo- 
pocrinide the genera, Cyrtocrinus, Schlerocrinus, Tetanocrinus, 
Gymnocrinus, Eugentacrinus, Phyllocrinus and ? Tormocrinus. 
9 Zeitschr. d. Deutsch geol. Gesell. XLIII, Heft 3, p. 612. 
