234 LE. Billings on the structure of Crinoidea, Cystidea, etc. 
closed. Five minute grooves radiate out to the extremities of 
the five angles of the disc. These grooves are identical with 
those of Pentremites ed Nucleocrinus and were occupied by 
the ovarian tubes. The ambulacral canals of the true Crinoids 
and of the Star-fishes are represented in a rudimentary condi- 
tion, in this species, by the wo As cra s which open out to the 
surface through the ten fissure-like spiracles, s. The oro-anal 
orifice is interradial. C. stelliformis in external form, the inter- 
radial Ios Bip of the mouth, and the closed ambulacral a. 
true org Its affinity to Codaster was first pointed out 
by Dr. C. A. White, who also “aia that it should be as- 
signed to a distinct era (Bost. Jour. N. H., vol. vii, pp. 
486, 487). The main nce rertaiotn the Cystidea and ie 
' Blastoidea i is, that in the airnase the hydrospires do not com 
municate with the pinnule, whilst in the latter the caniiaée 
of the pinnul and hydrospires are directly connected by the 
ambulacral pores. 
The developement of the recent Crinoid Antedon rosaceus, 
as described by Prof. Wyville Thomson (Phil. Trans., 1866), 
pursues a course that could not possibly result in the —. 
tion of such an animal as Actinocrinus. The aenideinke yey 
ae we cannot be said to be interradial in its position. 
cent Crinoid originates within the pseudembryo, — 
Eeclopen a mouth, vent and — of its own, all quite 
tinct from those of its nurse. 8 new, or permanent sone 
is for a ae time both oral and anak in its function, but al- 
though in this respect it resembles that of Actinocrinus, its po- 
sition in the center of the ambulacral system, shows it to 
Scale the mouth of the adult Star-fish, while that of Actino- 
rather homologates with the oral ‘orifice of the Bipin- 
starve At no time during its development does the ventral 
perisome exhibit the structure of that of the paleocrinoids, 
1. €., no orifice in the ambulacral center, and at the same time 
one in an interradial space. In the central position of its mouth, 
d in the possession of an cesophageal ring, Antedon stands 
