184 PALJEONTOLOGY OF NEW YORK. 



little less than one-half the length ; sometimes irregularly disposed, but usually 

 in longitudinal rows, alternating and forming oblique transverse rows, the 

 two arrangements being equally conspicuous. The peristomes are usually 

 very slight or obsolete, the intermediate space flat or convex, the apertures 

 appearing immersed ; sometimes the peristomes are comparatively strong 

 and the intermediate space slightly concave, the surface often presenting a 

 confused appearance. The surface is nodose, nodes sometimes irregularly 

 disposed, at other times there is a single row between adjacent apertures, 

 usually surrounding the aperture, but sometimes disposed in straight lines, 

 resembling ridges, and frequently partially obscuring the cell apertures. In 

 the process of growth these nodes form minute tubuli between the cells. When 

 the frond is worn or macerated the nodes are partially obliterated and the cell 

 apertures are much more conspicuous than in a perfectly preserved specimen. 



This species most nearly resembles T. (0.) transversa, and it will • sometimes 

 require a careful examination to distinguish them, but the branches are more 

 slender, and the cell apertures more elongate-oval. Internally the cell tubes 

 are not regularly curved. From T*. (0.) interplana it may be distinguished by 

 its more elongate-oval cell apertures and their closer disposition. From other 

 species of this geological formation it is distinguished by its elongate cell aper- 

 tures, generally surrounded by a row of comparatively prominent nodes. 



Formation and localities. Hamilton group, near Canandaigua Lake, and shore 

 of Owasco Lake, N. Y. 



Tkematopoka (Orthopora) ornata, n. sp. 



PLATE LV, FIG. 1 ; AND PLATE LVI, FIG. 4. 



ZoAKiUM ramose, solid ; branches 1 mm. in diameter. Cells tubular, arising 

 from the centre of the branch. Cell apertures oval, length about .20 mm., 

 width a little less than one-half the length, disposed in longitudinal, par.allel 

 rows, alternating and forming oblique transverse rows, at an angle of forty- 

 five degrees to the axis of the branch. Peristomes very thin, scarcely 

 elevated. Surface between the apertures elevated, obtusely angular, and 

 with numerous irregularly disposed nodes. 



