80 



the same as in P. gcmmiformh, the difference in size and form 

 simply gives the difference in the shape of the calyx which is 

 much more contracted in the superior part of this species than 

 in that one. The form of this species is such that the arm 

 blades must be shorter than in other species, and smaller in 

 proportion to the size of the body, or they must spread above 

 the mortises or articulating facets, differently from other species. 



Pound in the Niagara Group, near St. Paul, Indiana, and 

 now in the collection of Wm. F. E. Gurley. 



PISOCRINUS MILLIGANI, n. Sp. 



Plate V, Fig. 27, side view of a complete specimen which also 

 preserves part of the column magnified two diameters; 

 Fig. 28, basal view of the same specimen magnified 

 two diameters. This specimen does not show the 

 sutures in the calyx. Figs. 21, 22 and 23, 

 on Plate VI of the I7th Report of the 

 Geological Survey of Indiana be- 

 long to this Species. 



Species medium size, larger than P. gorbyi, which it re- 

 sembles. Calyx obpyramidal, truncated below and has a deep 

 columnar pit, and more or less rapidly expands in the radial 

 ragions, giving to the upper part a pentalobate aspect. There 

 is some difference among the specimens as to the proportions 

 in length and breadth and as to the extent of the peutalobate 

 extensions; but the specimens illustrated here and in the In- 

 diana report are average in this respect. P. gorbyi is longer 

 in proportion to the diameter than this species. Plates thick; 

 surface smooth. Column small and round. 



The five basal plates form a triangle that occupies the basal 

 cavity and the lower part of the calyx so as to be seen in a 

 side view even plainer than they can be in F. gorbyi. The 

 subradial and radial plates are proportionally shorter and 

 wider than in P. gorbyi and the lobate character more pro- 

 nounced. The radials are excavated by a wide dove-tailed 

 mortise on the lobes of the calyx, and, in the depressions be- 

 tween the lobes, curve in over the calyx so as to leave the 

 summit, when the arm blades are removed, with a five-rayed 

 star-like opening. There is no vault plate. The tenons of the 



