Spkctes ok TiiK Keokuk Ououp. 197 



apart which is the width of the nodes. The bands themselves are extremely 

 narrow. There is no such prominent development of bundles of lateralia as 

 in the typical species of Piiysosponoia, a fact which, of itself, is suggestive of 

 probable different generic relations in this species. Some small portions 

 of the skeleton which have been submitted to microscopic examination show 

 very large pentactins with blunt extremities, stich as are shown in figure 

 45. These were probably at the junction of the larger transverse and hori- 

 zontal })ands. There are also small, echinate pentactins or tetractins, some 

 larger fragments indicating similar spicules of more conspicuous size, and 

 small sausage-shaped diactins. The little cleme represented in the figure 

 shows the extreme minuteness of certain elements of the skeleton. Throtigh- 

 out the mass examined are clusters of minute spheres of pyrite, which at 

 first impression would seem of concretionary origin ; it may, however, be pos- 

 sible that these are modified spicules (diactins ?). No evidence has been found 

 of the umbels (clavules), anchors and plumes of Physospongia Dawsoni. 



LocaUtij. In the soft shales of the Keokuk group, Crawfordsville, 

 Indiana. - 



