434: 



ItEPORT OB' THE StATE GeOLOGIST. 



a recent and fossil state, are ornamented with ridges, granules, 

 nodes or spines ; the latter frequently hollow. In the course of 

 growth, as illustrated by ^g. 14, as layer after layer is added. 



Fig. 14. An enlarged section of Fenestella, showing minute tubuli and large pores. 



these hollow nodes, as seen in a transparent section, assume the 

 appearance of tubuli. These have been likened by some authors 

 to the "Acanthopores " of the Montioultporid^ ; but I think that 

 in most cases too much importance has been given to them, and 

 that in reality they are only ornamentations. The deposit of cal- 

 careous matter continues after the animals in the immediate 

 vicinity are dead, and all ornamentations of the surface are 

 obliterated, it presenting a uniformly smooth appearance. The 

 difference in appearance between the younger and more aged 

 portions of a Fenestelloid frond, and this applies to other forms 

 also, is often so great that seen in different fragments they would 

 be considered as belonging to two species. In the noncellulifer- 

 ous face of some Fenestelloid forms there are frequent, small, 

 circular pores with raised margins or peristomes, and in some 

 forms, as Fenestkapora and Isotrvp^, there are more conspicu- 

 ous apertures, frequently larger than the cell apertures. In 

 Fenestkapora the ridge' (carina) dividing the two ranges of cells 

 is also poriferous. The purpose of these pores have not been sat- 

 isfactorily accounted for. 



It has been suggested by Prof. Nicholson that the larger pores 

 may have been the bases of avicularia; if that explanation 

 should be accepted the smaller pores might be considered as 



