180 



G . W. SHRUB SOLE FURTHER NOTES ON 



Fenestella fossula, Dana, Geol. U.S. Explor. Exped. p. 710, pi. ii. 

 fig. 3. 



plebeia, d'Orbigny, Prod, cle Paleont. strat. t. i. p. 152. 



irregularis, Phill. Geol. Yorkshire, pi. 1. figs. 21, 22. 



retiformis, Schloth., King's Perm. Foss. pi. 2. rigs. 8-19. 



trituberculata, Prout, Trans. Acad. St. Louis, vol. i. p. 228. 



undulata-, Phill. Geol. Yorkshire, pi. i. figs. 16-18. 



virgosa, Eichwald, Lethaea Rossica, torn. i. p. 358, pi. 23. 



fig. 9. 



Gorgonia antiqua, Goldf. Pet. Germ. p. 99, pi. 36. figs. 3, ajj. 



Sp. cliar. — Polyzoary a flat expansion, slightly convoluted, circular 

 or oval in outline, depressed in the centre, by which it is attached. 

 Interstices regular on the obverse face when well preserved, somewhat 

 rounded otherwise, sides angular, keeled. Dissepiments thin, expand- 

 ing at junction with interstice, more markedly on obverse than re- 

 verse face. Fenestrules regular, oblong, equal to width of interstice 

 on obverse face, twice the width on reverse face ; four in the space of 

 two lines longitudinally, and six fenestrules in the space of two lines 

 transversely. Keel rounded and strong, with two or three nodes in 

 the length of a fenestrule. Pores round, prominent, their diameter 

 apart, two or three in the length of a fenestrule, and often one more 

 prominent than the rest in the angle formed by the junction of the 

 dissepiment with the interstice. 



Obs. This species, whether from Scotch, Irish, or English localities, 

 is everywhere the predominant form of Fenestella. It attained to 

 the largest expansion of polyzoary of any of the species. It de- 

 serves in every way to be regarded as the typical species of the 

 Carboniferous varieties. I have traced its growth through all its 

 stages, from a speck with two interstices on a stalk which clasped, it 

 might be, the spine of a Procluctus or a fragment of Serpula, to the 

 adult form with its strong and numerous rootlets. The early leaf- 

 like growth on a footstalk soon underwent a change ; the footstalk 

 became one of many rootlets, and the polyzoary coralliform at the 

 base, and ultimately a more or less circular expansion, the edges of 

 which terminated in slightly convoluted lobes. Its attachment to 

 the rock was secured by a cluster of rootlets from about the base, 

 and, indeed, from any part of the polyzoary which offered convenience 

 of attachment. 



The actual size to which this species attains it is difficult to 

 estimate, owing to the cleavage of the shale in which it occurs. I 

 have seen indications which lead me to believe that an adult poly- 

 zoon might attain a diameter of nearly two feet. Specimens of 

 this species will be found to differ from each other somewhat in 

 appearance. This I have found is more owing to the nature of the 

 matrix in which it has been imbedded than to any other cause. 

 The more calcium carbonate present in it, the fuller and more life-like 

 the organism appears, while it is flat and shrunken in the ordinary 

 black aluminous shale of the Carboniferous beds. 



In diagnosing the species the first thing to be noted is the size of its 

 interstice, in which it is intermediate between Fenestella nodulosa, 



