ON SOME FOSSILS FROM THE ISLANDS OF FORMOSA & RIU-KIU. 7 



another portion of the same section as seen by reflected light with 

 a black back-ground. The fossil is identical with the " chambered 

 organism " referred to in the notes mentioned above and proves to 

 be an undescribed species of Bryozoa of the genus Cellepora which 

 we designate, from the place of its origin, Cellepora formosensis. 



It is notoriously difficult to distinguish accurately for purposes 

 of diagnosing species, the " characters " of fossil specimens of 

 such Bryozoa as the Celleporœ. This is so even in the case of 

 specimens from beds such as those of the English Coralline Crag 

 where the fossils have suffered no very great change in their 

 calcareous parts during the process of fossilization. It is more 

 especially difficult where, in cases like the present, the organisms 

 have become thoroughly mineralised and all the chambers have 

 become filled up with crystalline calcite. 



By cutting such a specimen however in two directions at 

 right angles to each other and viewing the polished surfaces as 

 solid objects by reflected light it is possible to see some of the 

 characteristic features of the individual cells. This is made possible 

 by the feet that the polished crystalline calcite reveals the micro- 

 scopic structure for a short distance below the surface and so the 

 apertures and other features of some of the earlier formed cells, 

 which have become imbedded but not altogether obscured by the 

 subsequent growth of overlying chambers, are brought to light. 

 In a word the presence of clear crystalline calcite in the chambers 

 of the fossil, to the exclusion of an opaque substance, furnishes 

 an approach to the opportunity for examination by section which 

 is given by the comparatively unaltered Celleporse from the English 

 Crags. Failing a cut and polished surface of a crystalline specimen 

 it has been found serviceable to examine as an opaque object an 

 ordinary microscopic section if it be not cut too thin. 



