188 



Gr. W. SERTJESOLE — FURTHER NOTES ON 



mutilated and altered fragments of the polyzoarium in all stages of 

 its growth, not only of Fenestella, but of Ptylopora, Glauconome, 

 and IcJitJij/orhachis, all of which presented a reticulated character., 

 which under certain conditions might have been (and, indeed, has 

 been) mistaken for that of Fenestella. Hitherto it has been the practice 

 to assign any free fenestrate fragment of a polyzoan to Fenestella. 

 With the discovery to which I have alluded, that Fenestella was not 

 singular in possessing a fenestrate polyzoary, the error of that 

 method of determining polyzoan fragments becomes apparent. 



The few species to which I have reduced the British Carboniferous 

 Eenestellidae is, I find, in perfect agreement with the results arrived 

 at on the American continent. Prout has published * a list of eight 

 species of Fenestella from the Carboniferous rocks of North America ; 

 although no plates are given, the details of the species are so minute 

 as to leave nothing to be desired in the way of description. Of 

 these eight species there is only one (Fenestella Norwoodiana) that 

 has any claim to be considered a new species ; they correspond exactly 

 Avith the types of our various English species. Prout did his work 

 without the aid of Prof. M'Coy's book on the Carboniferous Eossils 

 of Ireland, in which the Eencstellidoe are for the first time 

 adequately described. The result of Prout's independent research, 

 apparently with ample material, is that only five good species are 

 made out. These American synonyms I have placed for the first 

 time under their respective English species. 



There are possibly a local species or two of Fenestella which I 

 have not described. Fenestella liallcinensis is one of these local 

 forms. I have not met with it elsewhere than at Halkin Mountain. 

 These local species require to be very carefully worked out before 

 they can be definitely pronounced to belong to the Eenestellidse. I 

 would suggest, with a view to the prevention of a needless mul- 

 tiplication of species of Fenestella in the future, that, before descri- 

 bing a new species, the nature of the attachment of the fenestration 

 should be definitely ascertained, whether to a root-stalk with root- 

 lets, as in Fenestella, or to a midrib or stem, as in Ftylopora and 

 Glauconome . Nor do I consider this standard too high. I have 

 adopted it with the five species which I have described. Owing to 

 the complicated surroundings which I have shown to be connected 

 with Fenestella and the forms allied to it, I am strongly of opinion 

 that some such course of procedure is necessary. 



The following table of the measurements of the leading features in 

 the several Fenestellce will be found of considerable service in es- 

 tablishing their identity. 



* Trans. Acad. St. Louis, vol. i. p. 228-236. 



