THE CARBONIFEROUS FENESTELLTD^E. 



183 



Locality. This species is comparatively rare in the Mountain- 

 Limestone beds of England and Scotland, and very abundant in 

 certain localities in Ireland. 



Fenestella nodulosa, Phill. Geol. Yorks. pi. i. figs. 31, 32, 33. 



Fenestella bicdlulata, E. Eth., Jim., Mem. Geol. Surv. Scotl. Sheet 

 23, p. 101. 



■ frutex, M'Coy, Syn. Garb. Eoss. Ireland, pi. xviii. fig. 10. 



Popeana, Prout, Trans. Acad. St. Louis, p. 229. 



subretiformis, Prout, Trans. Acad. St. Louis, p. 233. 



Sjp. char. — Polyzoarium, early growth folia ceous, having a distinct 

 stem or footstalk, becoming an oval or circular expansion. Inter- 

 stices regular, rounded, carinated and bifurcating ; remains of spiny 

 processes along the keel. Dissepiments thin, rounded, regular, a 

 little arched in the early stage, not so thick as interstices. Fenes- 

 trates square, regular in the early growth, four fenestrules in the 

 space of one line measured longitudinally, and four fenestrules in 

 the same space measured transversely. In the later and upper 

 growth there are three fenestrules only each way in the same 

 measurements. Cells small, round, their diameter apart, one com- 

 monly at the end of each dissepiment, and one between, or three 

 to each f enestrule : this is in the early growth ; the later growth 

 has four in the same space. When the cells occur in the angle 

 formed by the junction of dissepiment with insterstice, the former 

 is expanded at the point. This feature is not constant. Cell-mouth, 

 when preserved, nearly on a level with the keel. 



Obs. This is a very marked and easily recognized species ; its 

 square fenestrules and the round-wire-like nature of the interstices 

 and dissepiments on the reverse face at once distinguish it from all 

 others. In mature specimens the reverse has a peculiar and 

 characteristic nodular aspect. In size it is somewhat minute, 

 being intermediate between Fenestella membranacea, Phil., and 

 Fenestella plebeia, M'Coy. Both Phillips and Prof. M'Coy were 

 unfortunate in the fragments which they selected for description * 

 it is not surprising, therefore, that when a good representative 

 specimen was found it should be described as a new species. 

 Hence by far the best description of Fenestella nodulosa, Phill., is 

 that given for Fenestella bicellulata, E. Ether., jun. 



In 1874 Dr. Young and Mr. John Young announced the disco- 

 very of a new Carboniferous polyzoon, Actinostoma fenestration, in 

 which we have all the characters hitherto observed by Phillips, Prof. 

 M'Co} T , and Mr. E. Etheridge, Jun., in Fenestella nodulosa, with the 

 addition of the cell-aperture terminating in a nipple-shaped pro- 

 jection, the orifice of which was furnished with eight radiate denti- 

 cles. To regard Actinostoma as the full development of F. nodidosa 

 seemed the right course : as such I alluded to it in my former 

 paper on the Carboniferous Eenestellidse. Since then Mr. Gr. E. Yine, 

 a most accurate observer of the palaeozoic polyzoa, informs me that 

 he has noticed the denticulate cell-aperture in Fenestella jplebeia, 

 M'Cov; while recently Mr. John Young, F.Gr.S., in a paper read 



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