186 



e. W. SHRUBSOLE FURTHER NOTES 0]ST 



measured transversely, and two fenestrules in the space of two lines 

 longitudinally. Keel rounded and well developed, marked along its 

 course with numerous spiny processes. Pores small and round, 

 their own diameter apart, prominent when preserved, from five to 

 nine in the length of a fenestrule. 



Obs. This is the largest species of Carboniferous Fenestella, as 

 regards the size of its interstice and fenestrules, although not so as 

 to the ultimate growth of its polyzoary, which is considerably less 

 than that of F. plebeia, M'Coy. This peculiarity at once dis- 

 tinguishes it from an y other species. It is subject to considerable 

 variation, and will be met with both larger and smaller than the 

 one described. Prof. M'Coy, in his arrangement of the Fenestellce, 

 assigned the smaller type to Phillips's F. polyporata, and the type 

 with the larger development and greater number of pores he de- 

 scribed as F. multiporata ; but as both conform so well to the type in 

 other respects, there is no reason for this division. This species 

 often, on the reverse, attains to the size and character of some of the 

 Folyporoe, from which it may readily be known by having only a 

 double row of pore-cells. 



Fenestella polyjporata never occurs very freely in any locality, but 

 seems generally distributed throughout the Carboniferous strata. 



Pexestella crassa, M'Coy, Syn. Carb. Eoss. Irel. pi. xxix. fig. 1. 



Fenestella laxa, Phill. Geol. Yorks. pi. i. figs. 26-30. 



My previous notice of this species was limited to the extent of 

 showing the identity in character between the species respectively 

 described by Phillips and Prof. M'Coy as Fenestella laxa and 

 Fenestella crassa. Since then a wider acquaintance with the Car- 

 boniferous Polyzoa, and more especially with the Irish species in my 

 possession, has caused me to hesitate about including it among the 

 Fenestella?, since I have good reason for believing that the frag- 

 ment which has been described as such will be ultimately found 

 to belong to another fenestrate genus of Polyzoa. The original 

 drawing of this species by Phillips clearly included two species of 

 Polyzoa — one a Polypora with three rows, and the other apparently 

 a Fenestella with two rows of pores — the latter from Ireland, be it 

 remembered, where in certain localities Ichihyorhachis Ncivenhamii, 

 M'Coy, and Glauconome grandis, M'Coy, are not uncommon. 



Specimens in my possession lead me to say that I have little 

 doubt of being able to show that the fenestrated form described as 

 Fenestella crassa, M'Coy, is likely to prove to be the network or 

 polyzoary of one or other of the above species, or some kindred 

 form. 



A glance at the drawings of Fenestella crassa given by Prof. M'Coy 

 would seem to confirm this view. The coarseness of the interstice, 

 and irregularity of the dissepiment and growth generally, are not 

 characteristic of the Penesf ellidge. Its true affinities have yet to be 

 ascertained. Por the present it is enough to say that its claims to 

 be considered a Fenestella are very doubtful. 



