Hamilton Group 



193 



GENUS PRISMOPORA, nov. gen. 



Bryozoum, consisting of triangular branches, frequently forming 

 irregular masses , sides equal or unequal, subangularly concave, cel- 

 luliterous on each face : cells arising from internal plates which radi- 

 ate from the center to each angle; angular margins non-celluliferous. 



Pjiismopora dilata, n. sp. 

 Branches frequent, sometimes rapidly widening and becoming flab- 

 ellate ; sides equal or unequal ; width of sides from 4 to 7 mm., inte- 

 rior intercellular space vesiculose; cells opening directly outward, or 

 slightly oblique to the surface, apertures irregularly disposed, diameter 

 .33 mm.; width of non-celluliferous margins .33 mm. 



Locality — Near Leonardsville, N. Y 



GENUS SEMIOPORA, nov. gen. 



Bryozoum flat, branches infrequent, sometimes bifurcating, at othei^ 

 times, trifurcating ; margins essentially parallel ; celluliferous on both 

 sides ; cells arising from a mesial epitheca; apertures circular or oval, 

 arranged in longitudinal parallel rows, ranges separated by a distinct, 

 continuous ridge ; and between the cells in a longitudinal direction, 

 are two minute pits ; apertures nearest to the margin larger and 

 more oblique than the others; a marginal space non-celluliferous, stri- 

 ated. 



Semiopora bistigmata, n. sp. 

 Width of branches 2.50 mm.; greatest thickness 60 mm., aper- 

 tures broadly oval, nearly parallel with the surface; length of aperture 

 .33 mm., arranged in parallel longitudinal rows, eight rows in the 

 width of a branch, separated by a narrow angular ridge ; ncn-cellulif- 

 erous marginal space very narrow, striated. 



Locality — New York. 



GENUS ACROGENIA, nov, gen 



Frond ramose, proliferous, two branches proceeding from the trun- 

 cate termination of the previous one , base of each division conical, 

 terete above, strongly stnated, becoming flattened and celluliferous ; 

 transverse section of the completed branch lenticular, celluliferous on 

 each side ; a space at the margin non-celluliferous , cells arranged in 

 longitudinal rows, separated by ridges, apertures of middle of branch 

 smallest, those of each succeeding row becoming larger, 

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