30 Meek and Worthen on Paleozoic Crinoidea. 
So far as we are at this time informed, this organ has yet 
been very rarely observed in any other family than the Actino- 
erinide, though it was probably more or less developed in va- 
rious other groups. In one instance Mr. Pie found it 
the Blastoids. 
. Ambulacral canals passing under the vault in the Actino- 
crinide.—In the third and fourth Decades of descriptions and 
illustrations of the Canadian Organic Remains, Mr. Billings, 
the able paleontologist of the Geological Survey of the Cana- 
dian provinces, gives some highly interesting and instructive 
remarks on the ambulacral and other openings of the Paleozoic 
Crinoids, In these remarks he noticed, at length, some strik- 
while in the living Co matula and Pentacrinus, the ambula- 
cral canals are seen extending from the arm-bases across the 
surface of the soft skin-like ventral disc, to the central mouth, 
generally, if not always, covered by close-fitting, solid plates, 
showing no external traces whatever of ambulacral furrows ex- 
tending inward from the arm-bases ; and that in nearly all 
cases they are merely provided with a single excentric, or sub- 
central opening, often produced into a long tube which, like the 
vault, is made up of solid plates. He showed that there is no 
evidence whatever that the ambulacral canals, in these older 
types, were continued along the surface of the vault from the 
arm-bases to the only opening, whether subcentrally or late- 
rally situated iad that in cases where this opening is pro- 
duced in the form of a greatly elongated proboscis, or tube, 
such an arrangement of the ambulacra would be almost a phys- 
ical impossibility. Hence he concluded that the ambulacral 
all Sainiier with our numerous types of western Carboniferous 
Crinoids, in which they are very conspieuous, and we had never 
