1 54 MOLLUSCA. 



elevated to their present position by Milne Edwards. They look like 

 Corals, having minute cells either in branched, reticulated or incrusting 

 forms. They never occur singly. No organ of special sensation has 

 been discovered, and but one ganglionic centre. D'Orbigny enumerates 

 1,676 fossil species. One of the oldest known fossils, Oldhamia, is 

 supposed to be a Bryozoan, so likewise some of the Graptolites. The 

 most common Palaeozic form is Fenestrella. 



No. 758. Archimides Wortheni, Hall. 



Four specimens on slab. These remarkable Bryzoans, 

 having spiral axes, are from the Keokuk limestone (Sub-carbon- 

 iferous), Warsaw, 111. Size, 12 s 4. Price, $1.25. 



