﻿2C>6 NEW YORK STATE MUSEUM 



a common hydrospire and therefore no necessity exists for com- 

 munication of water channels before discharging into the hydro- 

 spires as in Blastoidocrinns. Hambach's drawing seems to 

 show that the water flow from each brachiole was kept distinct 

 until it entered the hydrospire. Figures 4 and 5 of our plate 1 

 show portions of the other two arms possessed by the type. The 

 remaining two arms had evidently been weathered away before 

 the specimen was found. They show similar characters to those 

 found in figure 3 but figure 5 is of additional interest, as it seems 

 to show a tendency to pass from an alternate arrangement of 

 ambulacra to an opposite arrangement. The point of the adam- 

 bulacral marked e is very close to the middle of the end of the 

 plate. As we pass to the left the plates become very markedly 

 more opposite in their arrangement. The orad end of figures 3 

 and 5 is at the right. 



Figure 1 of plate 2 presents a side view of the terminal area of 

 the pseudambulacrum already represented in plate 1, figure 3, and 

 with the same amplification. The food groove is clearly seen at a, 

 partly roofed over by the covering plates already noted. At c, d 

 and e the inner, vertical, closed edges of three hydrospires belong- 

 ing to the rear row of adambulacra, may be readily recognized. 

 The two hydrospires to the right of e have had their inner edges 

 weathered away and show the beginning of the sheetlike cavity 

 down and through which passed the surplus water of the bra- 

 chiolar streams. At / the surface of the deltoid has been car- 

 ried away and the character of the understructure of mineral- 

 ized sheets brought to view. A portion of the undersurface of 

 a deltoid x 10 is shown in figure 2 of this plate. At the left 

 of the center of this figure is an area that shows better the nature 

 of the respiratory sheets, for their thin edges may be clearly seen. 

 The line marked b in figure 1 separates the deltoid from a 

 bibrachial. Near the right end of this line are several openings 

 along the base of the deltoid. These are the exits of the hydro- 

 spires. They become larger passing in toward the older, longer 

 and deeper hydrospires. This is another indication of that 

 greatly increased outflow caused by the lateral water streams 

 already postulated. In some of the adambulacra shown in plate 

 1, figure 2 and in plate 2, figure 1, the lower outer edges are 

 not in contact with the deltoid. This is probably due to the fact 

 that the organic membrane which occupied this position and was 

 subsequently mineralized, has now been partly removed through 

 differential solution. 



