SPENCER NIAGARA FOSSILS. 6oi 



ties. The surface is also free from the papillae of Prof. Nichol- 

 son's species, and besides we have moderately frequent tubes 

 opening irregularly over the surface either at the summit or sides 

 of the nodulose masses. Besides this, the pores on the surface of 

 the laminae are apparent under the microscope, as their mineral 

 filling is somewhat differently colored from that of the rest of the 

 organism. 



The mineral matter is composed largely of dolomitic grains, 

 which, owing to the porous character of the organism, crumbles 

 easily. 



JPormaiioti and Locality. — It occurs in the upper Niagara beds at 

 Carpenter's limekilns, about two and a half miles south of Ham- 

 ilton, Ontario. 



Genus DICTYOSTOMA (Nicholson, 1875). 



In this genus the fossils are composed of undulating concentric 

 layers surrounding imaginary centres. These layers are traversed 

 by horizontal canals. From the upper surfaces of the laminae 

 conical points are developed which support the laminaj above (in 

 place of i)illars) without being amalgamated with them. The 

 exterior surface is apparently solid, except irregular rounded per- 

 forations which extend into the mass more or less vertically. 



DiCTYOSTOMA RETICULATUM, nOV. Sp. 

 Plate 6. Figs. 14 & I4a (enlarged vertical section) . 



This fossil is composed of concentric laminae, which, with the 

 interlaminar spaces, have a thickness of rather more than one 

 millimetre for every pair, each being about half that thickness. 

 On the edges there appear the mouths of horizontal canals tra- 

 versing the layers. From the upper surfaces of the layers numer- 

 ous hollow conical points or elongated processes extend to the 

 lower side of next layers, without being united with them. There 

 are about three of these points in every millimetre of length. Be- 

 sides these connections between the laminae, there are occasional 

 strong vertical pillars, at about every two centimetres apart, that 

 only extends from one layer to the next. In some specimens, 

 this last laminar support is wanting ; and in that case the speci- 

 mens so closely resemble Prof. Nicholson's description of D. tin- 

 dulatu?n^ from the Niagara formation of Kentucky, as to differ 

 only in the relative sizes of the masses, layers, and conical point. 



