250 G. W. SHETJBSOLE ON THE VARIOUS SPECIES OF 



species could be definitely determined, I have no doubt that 

 most of them would be included under the head of this species. 

 There is also an undoubted correspondence in many details between 

 this species and the F. rigidula, M'Coy. The main difference, and 

 that a serious one, is that Prof. M'Coy figures his species as having 

 a double row of small cells on the keel, while F. lineata has a single 

 row only of the prominences. I have exaniined many specimens of 

 Fenestella from the Dudley beds without finding as yet one having 

 the small double row of cells on the keel. The regular mode of 

 growth, and rigid straightness of the interstice and keel, at once 

 distinguish this species (F. lineata) from all others in the Silurian 

 group. 



Locality. Wenlock Limestone near Dudley. 



Eenestella intermedia, sp. nov. Plate XI. figs. 3, 3 a. 



>Sp. char. Polyzoary, extreme base solid and strong, somewhat 

 conical in shape, ultimately forming wide open expansions. Inter- 

 stices on the obverse face broad, full, and rounded, having for the 

 length of two or three fenestrules two rows of pores, succeeded by 

 widening of the interstice and three rows of pores. This is repeated 

 over the expansion. The three-row series of pores immediately 

 precede the bifurcation of the interstice. Eeverse, finely striated 

 longitudinally. Width variable, alternately narrow and wide. 

 Dissepiments thin, recessed, not expanding at junction with inter- 

 stice ; six dissepiments in the space of two lines longitudinally. 

 Keel thin and fine between the two rows of pores ; a corresponding 

 line winding between each line of the three-row series of pores. 

 Pores on the inside of the polyzoary small, circular, prominent, 

 level with the keel, their diameter apart, three between dissepi- 

 ments. Penestrules on the poriferous face very narrow, wider on 

 the reverse, nine in the space oi two lines measured transversely. 



Obs. This very fine species, which up to the present time has been 

 strangely overlooked, except that I find it as Fenestella ijatula in the 

 Woodwardian Museum, is by no means uncommon in the Dudley 

 Limestone. It is met with in two very different conditions^— first, 

 when worn down, in which case the interstice is bare and cylin- 

 drical, and at certain distances on the site of the keel are two or 

 three cell-openings. In this stage it is easily recognized by the cells 

 occupying the place of the keel ; while in the more perfect condition 

 of the polyzoon, the poriferous face of the interstice is broad, fiat, 

 and slightly rounded at the sides, and has two or three rows of 

 pores arranged in the manner described — not on the keel, as claimed 

 for F. rigiclula^ M'Coy, but in the place of the keel. This, I may 

 remark, is a unique feature among the British Penestellidse, no 

 similar appearance being on record. The contrast presented be- 

 tween the two conditions to which I have alluded — the broad 

 interstice with its irregular row of prominent circular pores and 

 fine delicate keel, winding in and out between them, and fenestrules 

 nearly obliterated by the spread of the interstice on the one hand, 

 and a bare round branch with worn-down cell- apertures and wide 



