New Species of Sponges. 



51 



3. Flaggy sandstone and shale, about 20 feet. 



4. Hard sandstone with quartz veins, 3 to 5 feet. 



5. Hard gray shales and calcareous and dolomitic bands, 

 with some layers sf sandstone — 800 feet or more. 



6. Apparently underlying these, and occupying a great 

 extent of the shore, are black, gray and red shales and thick 

 beds of gray sandstone, the latter appearing at Mt. Misery 

 and Lighthouse Point, and holding the Graptolites above 

 referred to. These beds must be of great thickness in the 

 aggregate, but they are possibly repeated in part by faults 

 and contortions. 



The sponges contained in Band 2 above, are apparently 

 confined to a small thickness of the shale, but in this are 

 quite abundant. They are perfectly flattened, and their 

 spicules are replaced by pyrite ; but in some cases they re- 

 tain the outline of their form, and have their root spicules 

 attached. The spicules were, no doubt, originally siliceous, 

 but they have shared the chemical change experienced by 

 other fossils in this bed, whereby they have lost their silice- 

 ous matter and have had pyrite deposited in its place. In 

 some cases, also, the pyritised spicules have been frosted 

 with minute crystals of the same substance, greatly enlarg- 

 ing their size and giving them a mossy appearance. This 

 pyritization of spicules, once pi'obably silicious, is not un- 

 common in palffiozoic rocks, and it arises from the soluble 

 condition of the silica in sponges, and its association with 

 organic matter, which, in some modern sponges, as in 

 Hyalonema, enters into the composition of the spicule itself. 

 These spicules, therefore, suffer the same change with the 

 calcareous shells associated with them. 



Many of the sponges in these beds have been entire when 

 entombed. Others are decayed and partially broken up, 

 and there are some surfaces covered with confused patches 

 of loose spicules arising from the disintegration of many 

 specimens. 



Some remarks are perhaps necessary here respecting the 

 appearance of sponges in different states of preservation. 

 Of course the original textures of sponges are different, and 



