Corals and Beyozoans of the Lower Helderbero. 145 



MICHELTNA, Be Koninck. 



MlCHELINA LENTICULARIS. 



(PLATE III, FiGS. 1, 2, 3, 5.) 



Michclina lentiadav'is, Hall. Twenty-sixth Rep N. Y. State Mas. Nat. Hist., 



p. 113. 1S74. 



Corallum forming small lenticular bodies, the lower surface the less convex, 

 and covered with a strongly wrinkled epitheca ; cells large and few, broadly 

 campanulate ^ partition walls thin, strongly striate longitudinally, with the mar- 

 gins denticulate — the number of striae and denticulations varying with the size 

 of the cell. 



In a specimen of twenty mm. in diameter, there are about twelve cells, the 

 larger ones somewhat more than six mm. in diameter. The entire height of the 

 specimen is about the same as the width. 



This is a very small species, seldom attaining a diameter of more than twenty- 

 five mm. This form with the large cells and their strongly granulose-striate 

 character, are distinctive features. 



Formation and localities. In the shaly limestones of the Lower Helderberg 

 group, near Clarksville and Schoharie, N. Y. 



FAVOSITES, Lamarck. 

 Favosites Helderbergije. 



(PLATES IV, V, VI.) 



Favosites Helderbergiw, Hall. Twenty -sixth Rep. N. Y. State Mus. Nat. Hist., 



p. 111. 1874. 



Corallum- growing in large, lenticular, depressed-convex or hemispherical 

 masses, base covered by a strongly wrinkled epitheca. Cell-tubes polygonal, 

 averaging about one and one-half mm. in diameter, their inner surface showing 

 evidence of a few strong longitudinal striae, and more frequently above the 

 mural pores ; mural pores in one or two ranges, comparatively large, circular, 

 with margins distinctly elevated ; cell-walls thin, but greatly increasing by silic- 

 ification ; transverse partitions strong, numerous, about three in a space equal to 

 the diameter of the cell-tube. 



In many specimens some of the cell-tubes are larger and less angular than 

 those surrounding them, being a little more than two mm. in diameter, with 

 thicker walls. A single specimen from Coeymans Landing has slightly 

 larger tubes on one portion, while in all the others the cells have the ordinary 

 characters. 



This species differs from the Favosites Niagarensis, which it resembles in the 

 the size of the cells, in having more numerous diaphragms, and in the mural 

 pores being on the lateral faces instead of at the angles of the cells. 

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