Spong Ida from New Brunswick. 85 



pore-like depressions may be seen as spaces filled with dark 

 homogeneous calcite. They are very minute, of different 

 sizes, and oval, square, or more or less triangular in outline. 

 There are no points projecting into them ; and neither septa 

 nor spiculate septa-like processes exist. 



Where abrasion has been carried on so as to destroy the 

 granules and partly to level the intermediate narrow processes, 

 the structures become very comprehensible. A reticulate ap- 

 pearance is presented, the white calcareous meshes of the 

 skeleton surrounding dark polygonal or oval spaces. The 

 breadth of each space or reticulation is from y^- to -^ inch ; 

 and the sides are formed by narrow irregular cylinders, whilst 

 the angles are swollen and faintly nodular. These nodular 

 parts are the bases of the external granules. No septa or pro- 

 jections resembling those of the Perforata exist. 



Slightly deeper abrasion and polishing exhibit indications 

 of the junction of the irregular cylindrical sides of the meshes, 

 sometimes at the nodules or angles, or in the midst of the 

 cylinder, one part being received into the other. The swellings 

 at the angles are less, but are still prominent features ; and two 

 conditions of the environed area are to be noticed : in one, and 

 the most usual, the space is filled with clear dark calcite, and 

 no structures are seen in it ; in the other a white or opalescent 

 film intrudes from the sides nearly to the centre, leaving there 

 a small circular space of dark calcite. This second condition 

 resembles an imperfect tabula belonging to an endotheca, such 

 as is present in Chcetetes. In many spaces there is perfect 

 occlusion ; but the texture of the substance thus simulating a 

 perfect tabula, is not that of the calcareous mesh, it is that 

 of infilling foreign matter. This is proved to be the case in 

 radial sections. 



The areas differ much in size ; but none are very large, nor 

 are any surrounded by sets of smaller ones in regular series. 

 Their measurements correspond nearly with those given on the 

 surface. 



At this stage of the inquiry, if a good illumination is em- 

 ployed, with a rnagnifying-power of about 30 diameters, the 

 latticework of the calcareous skeleton of the fossil, seen on a 

 deepish abrasion, is found to consist of separate elements con- 

 joined, each being resolvable into two prongs and a stem of 

 the same thickness and length; and at their junction a nodular 

 process or another stem exists. A triradiate or quadriradiate ' 

 spicule with straight or bent limbs irregularly papillary here 

 and there on the edge, is the element ; and at the extremities 

 of the limbs there are swellings not unlike frills, some being 

 rather convex there and others concave ; and the convexity 



