306 



Report of the State Geologist. 



Figure 25. Phragmodictya catilliformit. 

 A minor mesh bounded by rods and pentactins, with curved pentactins 

 or hexatins over the Interspace. (J. M. C. ) 



aid was contributed by the spicular bands of the periloph extending downward 

 beyond the periphery of the disc. This extension bears in some degree the 



ornamental features of the 

 lateral walls of the cup and 

 many of the stronger spicular 

 bundles of those walls were 

 continued into it. The term- 

 inal or lower edge of the peri- 

 loph is not regular, but where 

 the ridges come down from 

 above it is produced into short 

 radieiform extensions. 



Reticulum. The net-work 

 of the sponge is exceedingly 

 fine, and the subdivision very 

 uniform. There are no strong 

 bands of vertical or horizontal 

 rods, and it is often difficult to 

 find traces -of them except near the base. On the surface of the basal obcone, 

 however, the vertical or rather radial bands are very distinct, while the hori- 

 zontal or concentric bands are less so. 



Skeleton. The search for the spicular elements of the skeleton has shown 

 that the rhabdus of the gastral and anchoring spicules are small and few in 

 comparison with the other species whose spicular structure is known. The 



28 fine texture of the re- 



ticulum is due to quad- 

 rules, which for the most 

 part, seem to be outlined 

 by strong hexactins at 

 the angles, their arms 

 overlapping (fig. 26). 

 These have long, smooth 

 and acute branches. 

 There also appear to 

 have been pentactins or hexactins of great size with echinate arms, as indicated 

 by the large fragment shown in figure 29, but had they been abundant we 

 should probably know more of their form. The only other spicules of nota- 

 ble size are indicated by the slender fragments bearing long spinules, shown 



Fiar/RES 27, 28. Spicules of Phragmodictya catilliformis, x400. 

 In figure 27 are curved pentactins like those seen in figure 26. In one of these spicules 

 the arms end in knobs. 



Figure 28 shows other modifications of the parenchymal spicules. (J. M. C.) 



