248 G. W. SHRrBSOLE ON THE VARIOUS SPECIES OF 



Schists of Desertcreat, Ireland. Unfortunately, the reverse only was 

 exposed ; consequently the details by which alone it could be recog- 

 nized are unknown. The polyzoary, from its wide, nearly flat ex- 

 pansion, would seem to favour the supposition that it belongs to the 

 Carboniferous rather than the Silurian type of Fenestella. 



Coming now to speak of the species to be described, I may truly 

 characterize them as having strong individual features, which clearly 

 define them, not only from one another, but also from their congeners 

 in other formations. It will be seen that I have considerably re- 

 duced the number of species. In the state of uncertainty in the past 

 as to their real character, it is impossible to say to what extent 

 they may have been repeated. I by no means wish it to be under- 

 stood that I consider the present list as to the number of species 

 either fall or complete. There is work yet to be done ; the main 

 details, and character of Fenestella (Retepora) infundihulum (Lonsd.) 

 remain to be worked out. In addition, I have traces or fragments 

 of two other species, the details of which are not sufficiently complete 

 to warrant publication. One species is intermediate in size between 

 Fenestella lineata and Fenestella reteporata ; the other is much 

 smaller than any Fenestella I have yet met with from either Carboni- 

 ferous or Silurian formations. It has one hundred and twenty-five 

 interstices measured transversely to the inch. I would suggest that 

 it should be provisionally known as Fenestella dudleyensis. As re- 

 vised, the Silurian species of the British Fenestellidae will be as 

 follows : — 



Penestella rigidtjla, M'Coy, Brit. Pal. Poss. p. 50, pi. i. C. fig. 19. 



This species and Fenestella patida were first described in the 

 Cambridge Catalogue. I have not succeeded in tracing it either in 

 the Woodwardian Museum or elsewhere. The marked peculiarity 

 about it is the double row of small cells on the keel. This I have not 

 been able to verify. It is due to Prof. McCoy to state that Hall 

 describes an American form, Fenestella elegans, as having the keel 

 *' margined on each side by a row of small oval cells" *. I have 

 mentioned before that I regarded the character of this species as some- 

 what exaggerated. My reason for so saying is that Prof. M'Coy was 

 clearly in error in claiming the same exceptional cell- character for 

 some of the Carboniferous species, which have proved to be not true 

 cells, but prominences, the remains of a former ornamentation. The 

 difiiculty is not lessened in consequence of its being stated that the 

 cells are only half the size of the ordinary ones. Now Fenestella- 

 intermedia, it is true, does carry in part a cell on the keel, but then 

 it is of the same size as the other cells. I strongly suspect that this 

 feature of the inferior cell is very much overstated. The explanation 

 is probably the following : — Some years ago, what is now known as 

 a prominence on the keel of Fenestella, the remains of a spiniferous 

 ornamentation, was regarded in some way as a reproductive organ. 

 Lonsdale termed them " abraded vesicles " f, while Prof. King 



* Hall, Pal. New York, vol. ii. p. 164 



t Geology of Eussia, vol. i. App. A. p. 630. 



