LOWER HELDERBERG ROCKS. 
121 
Edriocriiius pocillifonnis (n.s.). 
Plate V. Fig. 8 - 12. 
Base hemispheric or subturbinate, often less than a hemisphere, external¬ 
ly smooth or finely granulate : upper margin scollopped with five 
large and one smaller depression for the insertion of the radial and 
anal plates. Interior more or less deeply concave, with depressions 
corresponding to those on the edge of the cup ; the concavity not 
parallel to the exterior convexity. Radial plates and arms unknown. 
\ 
This small species occurs in considerable numbers in the central part of the shaly 
limestone, varying in size from that of half a pea to more than half an inch, and 
of greater proportional differences in elevation. A few retain some evidence of their 
former attachment to other bodies, but for the most part they are quite smooth upon 
the exterior. This part of the crinoid appears to be composed of an exterior and an 
inner plate; the inner not corresponding with the outer one in its concavity, the 
.exterior form being given by the process of separation from its sedentary position, 
and the subsequent secretion of calcareous matter to form a smooth surface. In some 
instances the interior presents scarcely any appreciable concavity, and the entire 
basal portion is then much wider than high. 
These bodies are usually so small as to be overlooked, or regarded as unimportant 
fragments of crinoids; and are rarely seen in collections. 
Fig. 8. Basal view of a large individual, the proportional length being greater than usual. 
Fig. 9. Lateral view of the same. 
Fig. 10. Lateral view of a larger specimen. 
Fig. 11. Interior of the same. 
Fig. 12. Enlargement of the concavity of fig. 10, showing the depressions corresponding to 
the depressions in the margin and the concentrically striated surface. At each 
angle there is a slight depression or pore, which seems to communicate with the 
cavity between the basal and inner plate. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Helderberg mountains, Albany county. 
[ Paleontology III.] 
16 
