Corals and Bryozoans of thr Lower Helderberg. 175 



each other equal to the width of the midrib ; pores on all specimens seen, indis- 

 tinct ; two rows on the lateral branches with three or more on the midrib ; 

 length of largest specimen seen, seventeen mm. ; width of midrib .5 mm. ; 

 branches about one-half as wide as the midrib. 



This species is very rare and all specimens observed are imperfect and indis- 

 tinct ; as the specimens seen appear, they have the character of both Icthycra- 

 chis and Glauconome. 



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



THAMNISCUS, King. 

 Thamniscus variolata, n. sp. 



(PLATE XXII, FIGS. 34-46.) 



Bryozoum fruticose ; several stems arising from a common base ; stems fre- 

 quently bifurcating and spreading laterally, becoming very much widened be- 

 fore bifurcation, clavate, celluliferous on one side, smooth on the other or faintly 

 marked longitudinally from the cell-tubes within. 



Cell-tubes cylindrical, diameter at their aperture about .15 mm. ; length 

 three mm. ; for most of the distance nearly parallel with the branches, then 

 abruptly turning and opening directly outward ; a row on each side of a branch 

 opens laterally ; in some places, especially just above the bifurcations, they are 

 arranged in oblique rows — the distance between the rows about equal to the 

 diameter of an aperture ; the apertures forming the rows are contiguous, but 

 generally they do not seem to be arranged in any regular order, and are fre- 

 quently crowded ; inosculating ; margins much elevated ; length of longest 

 specimen seen, eighteen mm., greatest diameter two mm. 



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

 Thamniscus Nysa, n. sp. 



(PLATE XXII, FIGS. 47, 4S.) 



Several stems arising from a common base, frequently bifurcating, cellulifer- 

 ous on one side, smooth or obscurely striated on the other, expanding but very 

 slightly below bifurcations ; diameter of largest stem seen, a little more than 

 one mm. 



Cell-tubes cylindrical, opening directly outward, diameter of aperture about 

 .12 mm., margins distinctly elevated; regularly arranged in oblique rows across 

 the branches ; distance between rows equal to the diameter of an aperture ; the 

 cell-apertures forming the rows are nearly contiguous. 



This species can be distinguished from T. variolata (pi. xxii, figs. 34-46), by 

 the more nearly equal size of branches, not much enlarging below the bifurca- 

 tions, by the smaller cell-apertures and their more regular arrangement. 



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



