123. CONTRIBUTION TO 



bulacra being covered by pinule joints. From the condition of preservation, 

 little else can be made out by the use of an ordinary hand lense, nothing in fact 

 as to the manner of attachment to the pore pieces. 



Figure 28 is a view where the top has been ground off, down to the point of 

 greatest width of the ambulacra, hardly half the length of the deltoids. The 

 hydrospire folds and the pores are exhibited, as well as the shape of the lancet 

 piece in cross section. One ambulacrum has been removed. 



The specimen figure 29 has been ground down about the same depth but 

 is better preserved internally and shows well the groups of hydrospires, the am- 

 bulacral pores and the lancet canal. 



If there is a closed under-lancet canal it can not be made out in this speci- 

 men unless the walls of the inner hydrospire sacks of a paired group are in con- 

 tact which does not appear to be the case. The lancet tube appears a.s a minute 

 dot and smaller than in Orhlfreinltes itonnood! where the writer first learned of 

 its presence. In breaking Burlington cherts for casts of this latter species, af- 

 ter removing the beautiful mold of the visceral cavity, delicate curved rods 

 were seen free in the cavity in the matrix, broken away from the cast by the jar 

 of the hammer. Delicate as these acicular rods are, occasionally they remain 

 in place on the fossil. 



Figure 80 is an enlarged view of a paired group of hydrospires as they lie be_ 

 neath the ambulacrum. The inner, adjacent folds are separated too far in picture. 



Kaskaskia group, Breckenridge county Kentucky. 



Figures 31 and 32 are different views of a specimen whose ventral surface 

 is covered by a pyramid, the character of which is rather obscure. 



This much can be said of it with certainty that it is a five lobed elevation, 

 the lobes facing the deltoid plates and covering the spiracles and presumably 

 the anal oj)ening, but an apparent injury occurs at that particular place and the 

 opening itself is seen but filled by what appears to be the collapsed lobe of the 

 pyramid. Between the bases of the lobes the anibulacral grooves enter the pyr- 

 amid as tunnels, but at one of these re-entrant angles a low roofing over the 

 groove passes a short distance down the ambulacrum, the edges of it being seen 

 further down where the roof itself has been broken in. 



Kaskaskia group, near Bowling Green, Ky. 



Figures 33, 34 and 35 are dilferent views of a specimen in which the pyra- 

 mid has been mostly broken away but showing well the inner character of the 

 structure. It seems to be a two-story afi'air, or in other words, a double cover- 

 ing, the inner or lower one, rather flat and of sufficient area to overspread the 

 central stellate opening and pass outward down the middle of the ambulacrum 

 as a slender low roof over the ambulacral groove. The outer or upper covering is a 

 five lobed pyramidal structure surrounding the spiracles and, doubtless,, the 



