HARDWICKE'S SCIENCE-GOSSIP. 



53 



I have before me the fragments of a slab of car- 

 boniferous shale from the polyzoa beds of North Wales 

 (fig. 42). It is about four inches square, and the 

 average thickness is about one inch. The specimen 

 was sent to me by my friend, G. W. Shrubsole, 



character. On breaking my own across the middle 

 and otherwise mutilating it, I was let into the secret 

 of Fenestella growth, for I found on the broken sides 

 evidence that I have long sought for, and much more 

 than I ever expected to obtain. 



/ffi 9 1 



Fig. 48.— Infertile branch of Paly- 

 J>ora tuberculata. (Prout, Hair- 

 myres.) 



Fig. 49.— Infertile branches of Messrs. Young, 

 peculiarly developed on the margin of a Fenes- 

 tella, from Hairmyres. (My own cabinet.) 



F.G.S., and he had in his possession a slab even 

 larger still, but unfortunately he has failed in other 

 visits to the district of obtaining more of the same 





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prtrJUk. 



Fig. 50. — Palseocoryne attached 

 to Fig. 51. 



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Fig- Si- — Fenestella plebeia ; showing the interrupted development 

 of the fenestrules ; the entire absence of fenestrules at a, on 

 face on the back are partially developed fenestrules of the 

 character shown at b. Previous to being slightly rubbed down, 

 PalKOCoryne were attached of the shape and character of c. (In 

 my own cabinet.) 



Fig. 52.— Processes from side of Fenestella. (Mr. Shrubsole-'s ' 

 collection.) 



The general idea of Fenestella growth is, that it 

 was either cup-shape or flabelliform, springing from a 

 rooted base similar to the recent Retepora or the 

 Gorgonia. My belief is that this species at least was 

 recumbent in habit, and that it began life on some 

 fixed spot, and that from this point it gradually spread 

 over the soft muddy bottom. Its development in 

 one continuous plane, in either large or small frondsy 

 was dependent upon the quantity of sediment held in 

 solution by the waters above. It the water was 

 tolerably fine and free from much sedimentary matter, 



