42 PALEONTOLOGY OF NEW YORK. 



and closely disposed, very frequently in contact and always distant less than 

 the diameter of an aperture : margins strong, elevated, those of the outer 

 ranges projecting beyond the branch. Branches usually round, but some- 

 times decidedly angular. Diameter of specimens 15 mm. or more. 



The very frequent bifurcations and the clavate branches are distinguishing 

 features of this species. 



Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 



ThaMNISCDS FR0TICELLA. 



PLATE XXII, FIG. :« 



Thamnisctis fniiicella, Hall. Thirty-second Rept. N. Y. State Mus. Nat. Hist., p. 17G. 1879. 

 " Report of State Geolog-ist for 1882. Expl. pi. 22, fig. 33. 1883. 



ZoARiUM consisting of a main stem and lateral branches. Bifurcations frequent, 

 occurring, on the specimens observed, at intervals of about 4 mm. Br.anches 

 above the bifurcation 1 mm. wide, increasing to 1.50 mm.; clavate; non- 

 celluliferous face rounded, striated. The celluliferous face has not been ob- 

 served, but some of the branches of the non-celluliferous face have been so 

 much worn by maceration, that the bases of the cells can be seen. They are 

 numerous, three in the space of five mm., and irregularly arranged. 



Formation and locality. Lower Helderberg group, near Clarksville, N. Y. 



Thamniscus? Cisseis. 



I'LATE XXII, FIGS. 44-30. 



Thamniscus f Cisseis, Hall. Tliirty-second Rept. N. Y. State Mus. Nat Hist , p. 176. 1879. 



In part Thamniscus f Cisseis, Hall. Report of State Geologist for 1882. Expl. pi. 22, fig-.s. 23-30. 1883. 



ZoARiuM ramose, solid ; celluliferous on one face. Bifurcations occurring at 

 intervals of from 3 to 4 mm. Transverse section of a branch circular, 

 diameter 1 ram. Branches more or less curved; on the non-celluliferous 

 face marked by fine, numerous striae. Cells tubular, length about .75 mm., 

 regularly curving and gradually enlarging to the surface. Apertures circular 

 or Ijroiully oval, sometimes sub-polygonal from mutual pressure; diameter 

 about .30 mm. ; those nearest the margin are larger and more oval than the 



