20 



Family GAUKOCRINID.E. 



RETIOCRINUS ALVEOLATUS, 11. Sp. 



Plate II, Fig. 22, azygous view. 



Column comparatively large and pentagonal. Calyx pentagonal, 

 transversly. Basals extend bnt little beyond the column, deeply 

 sunken or bearing a pit at each lower lateral side and a convex 

 ridge directed to each adjacent subradial. Subradials longer than 

 wide, the superior angle reaching almost as high as the first 

 radials, and bearing four radiating rounded ridges, two of which 

 unite with the basals below, and the others with the adjacent 

 first radials. There is a large deep pit at each lateral angle. 

 These pits in the calyx look like the pits or pectinated rhombs in 

 Porocrinus. Our specimen is silicified, and the depth of these pits 

 or whether or not they pass to the inside of the calyx cannot be 

 accurately determined. The subradial on the azygous side bears 

 an additional ridge that extends upward to the large plates in the 

 middle of the azygous area. 



There are four primary radials in each series, rounded exter- 

 nally and, at first view, looking like free arms, but there are 

 small plates upon each side of the ambulacral furrow that unite 

 with a central balloon-shaped body exposing the small plates 

 in the interradial areas. There are four secondary radials in 

 each series and they are connected, internally, with the central 

 part of the body just as the primary radials are. The arms then 

 appear to become free and each one bifurcates again from the 

 fourth to the ninth plate, as near as the plates can be counted in 

 our specimen. Thus giving to the species forty arms. In the 

 azygous area there is a central row of large plates, looking like 

 an arm, that extends as high as the secondary radials, and is con- 

 nected with the central balloon-shaped body just as the primary 

 and secondary radials are, except, of course, there is no ambu- 

 lacral furrow, but a furrow nevertheless. The appearance of our 

 specimen indicates the continuance of the balloon-shaped body, in 

 the form of a proboscis, probably to the height of the arms, but 

 there may be some doubt about it, as the arms are so numerous 

 and so closely crowded together, that it cannot be clearly dis- 

 tinguished. 



