SPENCER NIAGARA FOSSILS. 599 



In this species, those specimens obtained at Hamilton have 

 their laminae much thinner than the spaces, there being two of 

 each for every millimetre in thickness. The spaces have been 

 completely filled w^ith supplemental matter. It is exceptional to 

 find specimens showing the nodulose surface, but numerous spe- 

 cimens exhibit beautifully the stellate impressions of the horizon- 

 tal canaliculi when the surfaces are polished. 



Foniiatioti and Locality. — The habitat of this species is in the 

 uppermost two feet of the Niagara-beds, exposed at Carpenter's 

 limekiln, two and a half miles south of Hamilton, Ont., where it 

 is abundantly found associated with C.botryoideum making up a 

 great portion of the bed of limestone ; but the organism is always 

 highly mineralized with dolomitic grains. This horizon is near 

 the top of the Niagara series. 



CCENOSTOMA RISTIGOUCHENSE, nOV. Sp. 

 Plate G. Fig. 12 (natural surface) and \ia (enlarged vertical section) . 



Large reefs composed of concentric layers penetrated by mi- 

 nute vertical tubuli, ending in the fine rounded granules of the 

 surface ; the connecting bars of the tubuli situated about as far 

 apart as their diameters, producing the appearance of horizontal 

 pores situated one above the other. Masses vertical, penetrated 

 by undefined canals, sending oft' many radiating canaliculi, thus 

 producing on the surface irregular depressions, bifurcating and 

 radiating among the papillar terminations of tubuli. These unde- 

 fined vertical canals are situated about one centimetre apart, and 

 in the same distance there will be found irregular rows of the 

 nodulose ends of twenty-five or thirty tubuli, in the centre of each 

 of which there is a depression. The thickness of the layers is from 

 I to 2.8 millimetres (where there is a tendency for the stone to 

 split horizontally), but in this distance there are from three to eight 

 horizontal cross-bars (between the tubuli), and the intervening 

 spaces of about the same size. 



The surface appearance resembles C. constellatum, but the 

 stellated canaliculi are much larger. Also, the ends of the tubuli 

 (shown on the surface) are much larger than in C. constellatufu, 

 and arranged often in undulating rows of perforated papillse. 

 There are no pores other than the tubuli. 



Formation and Locality. — This beautiful organism forms reefs of 

 two or three feet diameter in a fossiliferous limestone of the Up- 



