J83. CONTRIBUTION TO 



The entire dorsal cup as preserved is flat or even concave. The basal 

 plates on figure 7 occupy a shallow concavity while the rest of the calyx is flat.. 



Starting near the baso-radial suture a strong rounded ridge traverses the 

 radial plates to the periphery, bifurcating on the costals and growing stronger 

 outward. 



The number and shape of the interdistichal plates can not be determined^ 

 but such plates are present. 



The column was not large, but round, with a pentagonal canal. 



From the smaller specimen it would seem that the arms leave the calyx 

 horizontally, the interbrachials between the radial ridges turning up a little. 



The ventral disk, arms and anal tube unknown. 



The specimen No. 7 came from the Hamilton group at Speed's Quarry^ 

 Clark county, Indiana, and No. 8, is from the Upper Helderberg group at th.& 

 Falls of the Ohio. Collection of G. K. Greene. 



GENN^OCRINUS SIMULANS, N. Sp., (Rowley). 



Plate 54. Figs, 9, 10, 11. 



This species is founded on three calyces, more or less imperfect above. 



In the greater prominence of the basal plates our species resembles Aoro- 

 €?'itius. 



The radial series is traversed by a rounded ridge that bifurcates on the ax- 

 illary plates and passes to the arm bases. Two of these radial ridges fork at 

 the middle of the first radial and meet the basal expansion as an inverted v. 



The calicular areas between these ridges are flat, relieved only by small 

 central nodes from which radiate to adjoining plates, low fine ridges, as in the 

 drawings. 



Each plate of the interbrachial series has this delicate central tubercle with 

 the small radiating ridges. 



The column is medium and round. Columnar canal small and pentagonal. 

 The basal plates are three, expanding outward as in Aorocrinus, into a cleft 

 rim. Two of the basal expansions are slightly bilobed. The first radial i& 

 about as broad as long and hexagonal, its length being as great as both the 

 second and third radials. The second radial is hexagonal and a little broader 

 than long. The third radial is pentagonal and wider than long. The second 

 distichal is an axillary plate, the second palmer of one division being also a bi- 

 furcating plate and making thirty arms in all. 



The lowest interbrachial is hexagonal, a little larger than the second radiai 



