SPENCER NIAGARA FOSSILS. 597 



around centres or sometimes around the larger tubes themselves* 

 and do not exceed a tenth of a millimetre in diameter. These 

 pores extend down into the substance and sometimes appear to 

 traverse several thicknesses of laminae, and in a vertical section as 

 many as five pores with intervening four spaces occurring in the 

 length of one millimetre. The individual plates are scarcely dis- 

 tinguishable, as generally two or more are soldered by the sup- 

 plemental filling, so that the individual laminae are not separable 

 more than at from one-half to two millimetres apart ; but the 

 vertical pores, through this dense matter, being filled by differ- 

 ently colored matter, are conspicuous through the several layers. 

 The surface is too much worn to show any structures except 

 when polished. 



In the specimens that I have seen, the original matter is all 

 silicified. The specimen on which this description is based is 

 about the fourth part of a reef, fifteen centimeters in diameter, 

 given to the writer by Mr. A. E. Walker of Hamilton, who 

 obtained it from one of the lower beds of the Niagara forma- 

 tion at that city. This species bears a close resemblance to C. 

 hudsonica of Dawson, but differs in its rudimentary horizontal 

 canal system and the arrangement of the pores. There is also a 

 resemblance to the Devonian C. incrustans of Hall, but besides 

 the radiating canals there appears to be an absence of pustules 

 around the apertures on the surface. 



Caunopora mirabilis, nov. sp. 

 Plate 6. Figs. 10, lOa & lOJ. 



This organism has a hemispherical discoid form. Like other 

 species of the Strotnatoporidce^ it consists of a mass of concentric 

 laminae with their interspaces. These laminie are traversed by 

 the numerous pores which come to the surface. Besides these 

 there are two systems of tubes perforating the whole thickness. 

 The smaller of these two series has a diameter of about half a 

 millimetre, and are situated at from 2 to 4 mm. apart, and radiate 

 more or less from the centre of growth. These are lined with 

 strong calcareous walls. The other series consist of not numer- 

 ous vermiform calcareous tubes of larger size, at least more than 

 a millimetre or even two millimetres in diameter. These last 

 originate in the surface of a hemispherical calcareous nucleus, 



