280 Report of the State Geologist. 



(o) The Radial Pillar. — There can be no question that the 

 structure here called the radial tube or canal is the perpendicular 

 spicular ray of other writers. Inasmuch as it has been shown 

 that the five other rays of the spicule did not exist, it seems 

 illogical to denominate this structure in any sense a spicular arm. 

 The fact that the central canal is so large in comparison with the 

 surroundicg integument, taken in conjunction with the relation 

 of these bodies to the outer and inner walls, leaves little doubt 

 that they were really tubes and did not partake of the nature of 

 spicules. Moreover, the tubes appear to terminate at the bottom 

 of the rhombic pits, and this character both argues against their 

 original spicular nature, and suggests the probability that they 

 were never connected with a summit plate. 



III. The Poles. 

 In the Lower Helderberg specimens of E. infundibuliformis 

 the upper part has been destroyed, but the basal portion has, on both 

 its outer and inner surface, what may be called a polar region. 

 ]^either the number nor arrangement of the plates which lie 

 about the lower pole is indicated in specimens accessible to me. 

 If, as Rauff claims, the basal pole is the starting point of growth, 

 it seems unwise to deny as he does that HECEPTAcciLirEsand Isgha- 

 DiTBS occur as cup-like or saucer-shaped individuals, since they 

 must have assumed these forms as intermediate steps toward a 

 completely inclosed condition. 



IV. The Inner Wall. 

 It is agreed by Ra-uff, Hinde and Billings that the endorhin 

 is formed by the dilatation of the inner extremities of the radial 

 pillars. The wall is, then, theoretically, composed of plates, but 

 these are usually more or less united into a continuous surface, 

 and are not equivalent to the summit plates of the ectorhin. 

 HiNDE and Billings further agree in ascribing to this wall both 

 transverse and longitudinal canals. The latter are excavated in 

 the substance of each plate, and run between the middle points 

 of opposite sides. The transverse canals or pores are formed by 

 the truncation of the four angles of each plate. The juxtaposi- 

 tion of four plates produces the pore. The canals of adjoining 

 plates communicate with one another, thus forming a reticulation 

 of confluent channels in the wall. The pores served to connect 



