Spongida from New Brunswick. 89 



smaller limb by a frilled or irregular cup-shaped expan- 

 sion of a slightly larger ; and the line of suture is visible. It 

 often happens that the spicules do not quite touch, and the 

 expanded limb-end of one and the corresponding smaller ter- 

 mination of the other and opposite limbs are separated by a 

 microscopic interval. Sometimes one limb, frilled or digitate 

 or simply rounded, projects, without that of any other spicule 

 being near ; and deformed specimens of these solitary parts are 

 not unusual. Here and there the junction, as has been noticed 

 already, is by direct fusion ; and this occurs in the broad flat 

 spicules of the canals more than elsewhere. 



As the canals are close, and radiate to the periphery, in- 

 creasing in number by bifurcation not far from the limits of 

 the central space, each one must be surrounded by several 

 others. Four, five, or six canals may environ the canal 

 under observation ; and a tangential section closely reproduces 

 the appearance seen in abraded specimens when looking down 

 on the reticulate ends of the canal-skeleton from the outside. 

 Each canal is therefore polygonal in section (tangential) . There 

 is no duplication of the wall of a canal ; and this structure is 

 merely the space left by the interlacement of numerous sets of 

 spicules in longitudinal series. 



The symmetry of the parts of these spheroidal fossils is 

 great; and there is a very constant resemblance, in every part 

 and in different individuals, of the skeletal elements and their 

 disposition. 



No separate spicules differing from those already noticed 

 are present ; and the tubulation of the spicules is not seen. 



A superficial examination of the specimens would lead to 

 the belief of their being Perforata or Tabulata, amongst the 

 Actinozoa and Hydrozoa ; but the areolation and structure of 

 the skeleton is not that of the one, nor are there tabula? or the 

 peculiar hard parts of the other group. 



The shape of the skeletal element in the mass is not unlike 

 thatof some of the ft.o,t Manons or Jereas of the Cretaceous forma- 

 tion. The arms of the spicules do not bifurcate, however. In 

 the general arrangement of the spicules in the canal-systems 

 there is some resemblance to that in Turonia, and there is only 

 a slight one to that of Aulocopium y Oswald, which is the only 

 hitherto described Palaeozoic organism which resembles the 

 Tetraclade Lithistids. In this form, which is free, hemi- 

 spherical, and even sometimes spherical, there is a central 

 cavity. 



The resemblance is not sufficiently great between the new 

 form and Aulocopium to place them together in the same 

 classification : nevertheless there can be no doubt that both 



