MORPHOLOGICAL PART. 137 
tween the arms to their full length, which in Symbathocrinus is composed of 
elongate quadrangular pieces. The tube rests upon the upper faces of the 
posterior radials, and extends to the tips of the arms. Haplocrinus, as we 
understand it, has a simple anal opening, piercing the upper half of the 
posterior oral. Cupressocrinus has a well-defined aperture between the 
muscle plates of two adjoining radials, 
The anus of the Inadunata Fistulata has been observed in but a few 
instances, and then only in the Cyathocrinide, the Poteriocrinidx, and in 
the embryonic Hybocrinus and Carabocrinus. In all of these cases, the open- 
ing was apparently covered by a rather large, rounded pyramid of eight or 
more pieces, which resembles the anal pyramid in the Cystids. In Carabo- 
ermus, in which the ventral disk remains permanently in the larval state, 
2.5 
A i 
SX 
ee 
Fig. 1. Fic. 2. 
Carabocrinus. — Vig. 1. Ventral aspect. Fig. 2. Dorsal aspect. 
R=radials; R! = radianal; x = anal; zp = anal pyramid; 0 = orals. 
having five large orals similar to those of the Larviformia, and subtegminal 
ambulacra, the pyramid is excentric and directed upwards (Figs. 1 and 2 of 
the accompanying diagrams).* A similar anus was observed by W. R. Billings 
in Hybocrinus conicus. In Cyathocrinus we have observed the anal pyramid 
in several species, and found it located in all of them at the end of the tube, 
directed anteriorly (Plate VII. Figs. 11 ab and 12a). The anus of the Pote- 
riocrinidee, which we have seen in Poteriocrinus, Decadocrinus, and in several 
species of Seytalocrinus and Scaphiocrinus, is located at some distance from 
the top of the ventral sac, and invariably at the anterior side, sometimes 
* These diagrams were made after drawings by Mr. Walter R. Billings. The specimen of Fig. 1 is in 
the collection of Mr. J. Stewart, that of Fig. 2 in his own collection, 
18 
