112 Twenty- SIXTH Report on the State Museum. 



when perfect. Cell tabes averaging one-twentieth of an inch, poly- 

 gonal, their inner surface showing evidence of a few strong longitudi- 

 nal striae; the walls rather thin, but greatly increasing by silicifica- 

 tion ; the sides perforated by a single row of medium sized pores 

 communicating with the adjacent cells; transverse partitions numer- 

 ous, one, two, or sometimes three in a space equal to the diameter of 

 the tube, the margins bent downwards at the junction with the cell- 

 walls, and often perforated in one of the depressions. 



In many specimens, a few of the cell-tubes are larger than those 

 surrounding them, measuring about one-sixteenth of an inch, with 

 thicker walls, and being less angular. A single specimen from 

 Coeymans' Landing has slightly larger tubes on one portion, while 

 in all the rest the cells have the ordinary characters. 



The longitudinal strise seen on some silicified specimens are not 

 constant, and are not seen on calcareous specimens, and may be a fea- 

 ture produced in the process of silicification. 



This species differs from the Upper Helderberg form known as F, 

 hasaltica in the smaller tubes and more closely arranged partitions. 



Formation and locality. — In the shaly limestones of the Lower 

 Helderberg group, near Olarksville, Albany county. It is here 

 found weathered out from the rock and silicified, frequently in 

 masses of a foot or more in diameter. Smaller specimens of what 

 appear to be the same or a closely allied form occur at Cole's quarry, 

 in Herkimer count}^, IS^ew York. 



Favosites conica n. sjp. 

 Coral forming conical masses, flattened at the base, composed of 

 moderately large, strongly diverging, polygonal cells, curving more 

 abruptly towards the surface of the mass ; dividing walls thin, per- 

 forated by large, round, intercellular pores in one, two, or sometimes 

 three series : those series which consist of a single range have the 

 pores vertical one above the other ; in the series of two ranges, they 

 generally alternate with each other ; where there are a greater num- 

 ber, the pores are irregularly disposed : margins of pores are usually 

 slightly thickened. Transverse partitions closely arranged, two or 

 three in a distance equal to the diameter of the tube. Tubes very 

 variable in size and shape, some being not more than four-hun- 

 dredths of an inch in diameter, while many are an eighth of an inch ; 

 the larger cells are six or more sided, the smaller cells four or five 

 sided, or triangular, a feature not common in Favosites ; but the 

 triangular cells are usually small and near the base and soon become 

 pentagonal from the truncation of two of the angles. 



