THE CARBONIFEROUS FENESTELLID^. 



189 



Species. 



dumber 

 of pores 

 between 

 dissepi- 

 ments. 



Shape of 

 fenestrule. 



Number 

 of fenes- 

 trates in. 

 two lines 

 trans- 

 versely. 



Number 

 of fenes- 

 trules in 

 two lines 

 longitu- 

 dinally. 



Fenestella plcbcia, M'Coy... 

 racmbranaeca, Phill.... 



3-4 

 3-4 

 3-4 

 6-9 

 3-4 



Oral. 



Oblong. 



Square. 

 Elongate. 

 Elongate. 



6 

 8 

 6-8 



4 

 6 



t 



6-8 

 2 



4 



polyporata, Phill 



halkinensis, Shrubsole 



Discussion. 



The President stated that this group, which ranged from the 

 Llandeilo to the Permian, is often represented by very imperfect 

 specimens, and that there is great difficulty in discriminating the 

 forms. Nowhere are they so well preserved as in the Carboniferous 

 rocks of Flintshire and Scotland. 



Dr. Mtjeie spoke of the value of the method adopted Toy the 

 author in studying the varieties of growth and development in each 

 species. 



Prof. Seelet regarded the principle on which the author had 

 worked as a very sound one, and he thought that such revisions of 

 certain life-groups were calculated to be of the greatest service to 

 geology. 



The President remarked upon the difficulty that arises from the 

 fact that man}* type specimens are inaccessible for reference. He 

 deprecated the creation of new specific names before a rigid com- 

 parison had been made with the old ones. 



