138 DlCTYOSPONGID.*;. 



retained there is a small mass of sandy matrix adhering to the basal portion, 

 though the remainder of the cup so far as retained is cleanly separated from 

 the rock. From this it is perhaps to be inferred that the center was largely a 

 tufted pompon of spicules whose structure is obscured by complication with 

 the sediment. 



It is possible that the nonnal form of the cup was the reverse of that 

 we have suggested ; instead of being saucer-shaped, it may have been broadly 

 umbrella shaped. This is, however, less in accordance with the form usually 

 assumed by the palaeozoic Dictyosponges which have been described, but it 

 is a shape occasionally reproduced among living hexactinellids. The 

 material, however, representing the genus is insufficient for the detennination 

 of this point. 



From the center or basal point radiates a series of flat, gradually widening 

 ligulate bands, with elevated or thickened edges. These bands are approxi- 

 mately of equal size and are sube(juidistant, but a slight difference in the 

 interval between them at their origin becomes greatly increased toward the 

 margin. There is no evidence of more than a single series of these vertical or 

 radial bands, all of them meeting at the center. They are crossed by con- 

 tinuous concentric bands of similar character, though with a less palpable 

 thickening of the margins. These regularly increase in width as they recede 

 from the center, and the diameter of the intervals between them also increases, 

 but less rajiidly. At their intersection with the radial bands they do not lose 

 their definition, and are probably interwoven with them as there is no evidence 

 of their displacement at these surfaces, as would in all probability have 

 occasionally occurred had there been no actual connexion or interlacing of the 

 spicules. 



Over the interspaces between the radial bands it is observable that the 

 position or angle of these concentric bands is slightly changed ; they do not 

 there confonn to the general curvature of the surface of the cup but are 

 horizontal or approximately so ; the effect of this arrangement is to give to 

 each of these radial interspaces including the bounding I'ays a suggestive 

 resemblance to a much inclined step-ladder. 



The meshes or quadrides produced by the intersection of the two series of 

 bands usually show only clean rock surfaces ; one specimen however indicates 

 that these quadrules have had their angles filled by a delicate parenchymal 

 film which encroaches on the quadrules to such an extent as to leave a sub- 

 circular opening. We have no palpable evidence of the nature of the spicules 

 composing the radial or vertical, and the concentric or horizontal bands 



