Lower Helderberg Bryozoa and Corals. HI 



the fronds several inches in length. Cell tubes polygonal, very long 

 and slender, rising from the center of the branch and gradually 

 curving outward to the surface ; increased by interstitial additions ; 

 diameter of the cells at the surface of the branch about a hundredth 

 of an inch. Transverse floors or partitions distant in the lower part 

 of the tube, becoming more numerous towards the outer end, and 

 near the surface the distance from each other is less than the diame- 

 ter of the tube. 



In well preserved silicified specimens the cell walls on the surface 

 are comparatively thick, the margins slightly elevated at the junc- 

 tion of cells, but not spine-like, the young cells appearing in the 

 angles ; in the interior of the branches the cell walls are obliquely 

 corrugated. No maculae have been seen on the branches. 



This is a beautiful and not uncommon species. 



Formation and locality .^-lx\ the shaly limestones of the Lower 

 Helderberg group, at Catskill creek, near Clarksville, and at Scho- 

 harie, New York. 



Ch^tetes sph^rica n. sp. 

 Bryozoum growing in large convex or hemispherical masses, com- 

 posed of cell tubes radiating from w^ithin and diverging more rapidly 

 as they approach the surface of the mass. Tubes small, polygonal, 

 increased by interstitial additions ; transverse partitions three, four 

 or more times the diameter of the tube ; cell walls very thin and 

 corrugated. The surface of the mass is marked by maculae, situ- 

 ated about a fourth of an inch from centre to centre, composed of 

 cells which are about twice the size of the intermediate cells ; the 

 addition of new cells mostly takes place within the maculae. About 

 eight of the intermediate cells occupy the space of a tenth of an inch. 



This species grows in very convex masses of sometimes four or 

 more inches in diameter. On cursory observation it has the appear- 

 ance of Favosites conica^ with which it is associated, but it is com- 

 posed of smaller tubes which are destitute of intercommunicating 

 pores, and the transverse plates are more distinct, while also the 

 maculated surface distinguishes the species. 



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

 derberg group, near Clarksville, and on Catskill creek. 



Genus FAYOSITES Lam. 



Favosites Helderbergi^ n. sp. 

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

 spherical masses, with a wrinkled epithecal surface on the under side 



