MELOCRINIDZ&. 293 
suture, and form together rigid tubular appendages, which pass out from the 
calyx upwards. In some cases the connection of the appendages is inter- 
rupted for short distances, but, so far as known, all of them come together, 
and are united toward the upper part. From these appendages throughout 
their full length, at certain intervals, and from opposite plates (not alter- 
nately) are given off well defined biserial arms, bearing pinnules on alternate 
sides. A slight departure in the construction of the main trunks occurs among 
species in which the proximal arms are given off alread y from the first 
axillaries, 7. ¢. from the costals. In these species the trunks at the dorsal 
surface are composed of but a single series of plates, and the pinnule-bearing 
arms are arranged alternately as in Steganocrinus sculptus. The ventral sur- 
faces of the appendages are roofed over in all cases by rigid covering plates. 
Interbrachials numerous ; the first placed upon the sloping upper faces 
of the radials, followed by two plates in the second row at the four regular 
sides, three plates at the anal side, and a greater or less number of irregular 
plates above, which meet with the interambulacral plates. Ventral disk 
highly elevated or scarcely convex; the orals in some species largely de- 
veloped, in others indeterminable. Anus excentric and generally — perhaps 
always — extended into a small tube. 
Column round, composed of alternate long and short joints; axial canal 
small. 
Distribution. — Melocrinus ranges from the Upper Silurian to near the 
close of the Devonian, and is well represented both in America and Europe. 
Remarks. — The genus Me/ocrinus holds the same relation to Mariacrinus 
that Steganocrinus does to Actinocrinus, and Eucladocrinus to Platycrinus. In 
all these types the construction of the calyx remains relatively almost un- 
changed, while a remarkable modification occurs in the brachial appendages, 
which are extended into tubular rays with an indefinite number of semi-free 
brachials, giving off arms. 
Several attempts have been made to subdivide Melocrinus into two or 
three genera. Roemer, in 1855, proposed the name Castanocrinus for 
species with a central or subcentral anal opening, retaining Jelocrinus, with 
M. hieroglyphicus Goldfuss as type, for species with a lateral opening. Our 
examination of the various species leads us to doubt whether such a division 
can be practically upheld. We agree with Schultze * that the anus is never 
central in this genus, nor in any case actually lateral, but its position is 
* Monogr. Hifl. Kalkes, p. 63. 
