22 PALAEONTOLOGY OF NEW YORK. 



This species closely resembles C. vmusta of this formation, but may be dis- 

 tinguished lus follows: The branches of that species are hollow, the cell aper- 

 tures are slightly larger, more decidedly oval, often regularly arranged in quin- 

 cunx over a large portion of the specimen ; but there are occasionally specimens 

 which could not be separated by the surface characters alone. 



Formation and locality. In the shaly limestone of the Lower Helderberg 

 group, near Clarksville, N. Y, 



Callopoba pereleoans. 



I'LATE XII, FIGS. 10-17 ; AND PLATE XXIU A, FIG. M. 



CcUlopom pereUgans, Hall. Twenty-sixth llept. N. Y. State Mus. Nat. Hist., p. 102. 1874. 

 " '• Thirty-second Ropt. N. Y. State Mua. Nat. Hist., p. 154. 1879. 



•• " •• Report of State Geologist for 1882. Expl. pi. 12, tigs. 10-17. 1883. 



ZoABiCM fruticose, several stems arising from a common base; bifurcations 

 very frequent. Branches solid, diameter from 2 to 5 mm., generally from 3 

 to 4 mm. Cells tubular, arising from the center of the branch, gradually 

 diverging till within one mm. of the surface, when they abruptly turn out- 

 ward ; walls very thin. Septa infrequent or entirely wanting. Apertures 

 circular or sub-polygonal from pressure, diameter .50 mm, ; irregularly dis- 

 posed, sometimes in contjict ; at other times distant one mm. or more : mar- 

 gins thin, distinctly and equally elevated. Mesopores frequently longer than 

 wide, length sometimes four times the width : margins equal in thickness 

 and height to those of the apertures. Intercellular space occupied by septate 

 tubuli of varying lengths, occasionally extending to the center of the branch. 

 Septa very thin and frequent, from eight to twelve in the space of one mm. 



This species closely resembles C. elegantula of the Niagara group, and may be 

 only a variety of that species. Externally the mesopores of C. elegantula are 

 much smaller, and the width is usually about equal to the length. Internally 

 the cell-tubes have numerous septa nearly equal in thickness to the cell-walls, 

 frequently four in the space of one mm., while in this species the septae are 

 very infrequent or entirely wanting. 



Formation and locality. In the shaly limestone of the Lower Helderberg 

 group, near Clarksville, Albany county, N. Y. 



