SPENXER NIAGARA FOSSILS. 575 



drical calycles which penetrate the common canal (or ca?no£arc) 

 almost to the axis. The cells have their own distinct cell-walls; 

 they are cylindrical in form, about 0.5 mm. long and mm. o 35 

 in diameter. The portion of the cell towards the orifice overlies 

 the base of the next cell, so that there are from 25 to 32 calycles 

 in the length of a centimetre. More frequently only circular, or 

 ellipsoid, elevated (sometimes depressed) points mark the former 

 abodes of the polypites, which, being surrounded by a denser 

 texture, have not yielded to the pressure which has flattened the 

 walls of the common canal. The irregular striae and depressions 

 on the stipes and branches are probably occasioned by the une- 

 qual flattening of the canal and celluliferous portions of stipes. 



This species is the most easily obtained of the fossils of the 

 group, though good specimens are very uncommon. Generally 

 we must identify them by the relative size and arrangements of 

 the branches and filaments, or, in more perfect specimens, by the 

 form of the frond. 



Formation and Locality. — Since the geological survey of New 

 York first obtained this fossil in the Niagara shales at Lockport, 

 it has been found at Grimsby, and more particularly at Hamil- 

 ton, Ont., by Col. Grant, Mr. A. E. Walker, and myself, in the 

 earthy, magnesian limestones of the lower portion of the cherty- 

 bed, and in shaly rocks adjacent to it. (See geological section at 

 Hamilton.*) It also occurs near Louisville, Ky. 



DiCTYONEMA EXPANSUM, nOV. Sp. 

 Plate 2. Fig. 1. 



Frond flabelliform, composed of slender expanding and bifur- 

 cating branches, diffusely arranged, and united laterally by slender 

 filaments (often wanting) ; branches irregularly striated; texture 

 corneous. 



This species is clearly related to D. gracile in the relative size 

 of the branches, but these are much more diffusely and irregu- 

 larly arranged, with greater interspaces, which are from two to 

 four times the width of the branches. The transverse filaments 

 occur less frequently than in D. gracile. Fragments of this 

 species are not always easily distinguishable from D. gracile., 

 although the branches are looser and more spreading. The type- 



* In Paleozoic Geology of the Region of the West End of Lake Ontario, by J. W. Spen- 

 cer. Can. Nat., iS?2. 



