232 PALEONTOLOGY OF ILLINOIS. 



with three spicules of the layer next below it, it in like manner 

 supports, on the upper side of its node and arms three rays of 

 different spicules belonging to the series or layer next above. 



The Minnesota specimens, which are in a better state of preser- 

 vation than any others seen by me, exhibit at the surface great 

 numbers of exceedingly minute, apparently acerate spicules, 

 besides a small number of large Hexactinellids that are treated 

 of in the next paragraph. The minute forms may represent a 

 dermal layer, or so-called "flesh spicules;" or they may belong 

 to an altogether different sponge, in which case their associa- 

 tion with Hindia sphseroidalis would be purely accidental. 



On plate II, fig. 4c represents a magnified view of a large 

 Hexactinellid spicule, which is generally found with Hindia 

 sphaeroidalis, and not infrequently adheres to the surface of that 

 sponge. At one time I supposed, because of their association, 

 that they might belong to the surface layer of that species, but 

 since the totally different character of the spicules of Hindia 

 was ascertained, I have concluded that I was in error, and that 

 the isolated spicules belong to a very different sponge. They 

 resemble the regular six-rayed spicules of Hyalostelia, but as 

 yet, I have not found with them any of the rod-like, stellate, 

 nor anchor shaped spicules, which likewise occur (with the 

 simple Hexactinellid forms) in H. smithi Y. & Y., the type of 

 the genus. Provisionally, the spicules may be named Hyalostelia 

 solivaga. In searching a slab of Lower Silurian limestone from 

 near Cape Girardeau, Mo., for Bryozoa, I found smaller, but 

 otherwise very similar spicules. Such spicules are also occasion- 

 ally found associated with H. parva Ulrich, in the upper beds 

 of the Trenton in Kentucky. 



