CORALS AND BRYOZOA. 13 



reaching 5 mm.; diameter .20 mm. ; apertures slightly oblique to the surface. 

 Septa thin, infrequent. 



This species may be distinguished from C. abruptus [plate i.\, figs. 9-11], 

 by its fruticose appearance, its more .slender growth, (which character appears 

 to be constant), the thinner and more infrequent septa, but especially by the 

 manner in which the cell tubes approach the surface. 



Formation and localittj. Lower Helderberg group, Schoharie, N. Y. 



Ch^stetes (Monotrypella) abruptus. 



PLATE IX. FIGS. 9-11. 



Chcttetai abruptus, Hall. Thirty-second Kept. N. Y. State Mns. Nat. Hist., p. 148. 1879. 

 '• " " Report of State (Jeologist for 1882. Kxpl. pi. 9, tigs. 9-11. 1883. 



CoRALLU.M ramose, solid ; branches frequent, diverging at an angle of about 

 forty-five degrees. Cells tubular, polygonal ; arising from the center of the 

 branch and very gradually diverging until about 2 mm. from the surface, 

 when they abruptly turn outward. At this point they are generally con- 

 stricted, and the cell walls, previously very thin, become much thicker ; 

 length reaching 6 mm.; diameter at the surface from .20 to .25 mm.; 

 frequently spinulose at the angles. Septa rare or entirely wanting until 

 after the abrupt turning of the cell tubes, when they are numerous. 



This species, when a longitudinal section can be seen, is easily recognized by 

 the abrupt turning of the cell tubes to the surface, aLso in the constriction and 

 thickening of the walls at this point, features in which it differs from any 

 other species of this formation. 



Formation and locality. Lower Helderberg group, Schoharie, N. Y. 



