72 PALEONTOLOGY OF NEW YORK. 



The interior of this species has not been studied, but the exterior chanacters 

 are so diflferent from other Trematoporoid forms that there seems a necessity 

 of separating it as a distinct genus. 



Formation and locality. Upper Helderberg group, Onondaga Valley, N. Y. 



DIAMESOPORA, Hall. 1852. 



DlAMESOPORA CAMBRATA. 



PLATE XXVI, FIGS. 9, 10. 



Trenudopora camerata. Hall. Report of State Geologist for 1882. Expl. pi. 24, figs 9, 10. 1883. 



ZoARiUM ramose, lioUow ; branches 1.50 mm. in diameter; thickness of polyzoary 

 .50 mm. Cell apertures usually circular or slightly oval, sometimes arched, 

 diameter .33 mm. ; generally irregularly disposed, but sometimes forming 

 indistinct transverse rows. Anterior portion of peristome slightly elevated, 

 posterior margin strongly elevated, oblique. 



This species may be distinguished by its hollow cylindrical stems and very 

 oblique, somewhat scattered cell apertures. 



Formation and locality. Upper Helderberg group, near Caledonia, N. Y. 

 ACANTHOCLEMA, Hall. 1886. 



ACANTHOCLEMA ALTEKNATUM. 



I'LATK XXV, FIGS. 8-10. 



lyematopora cUUrnata, Hall. Trans. Albany Institute, vol. x, abstract, p. ti. 1881. 



AeeuUiloehma " " Repoi-t of State Geologist for 1885, advance sheets. Expl. i)l. 25, figs. 8-10. 



1886. 



ZoARiCM ramose, solid ; branches slightly more than 1 mm. in diameter. Cells 

 tubular, arising from a slender central axis, in contact for a little more than 

 one-half their length. Cell apertures oval, length about .20 mm., width two- 

 thirds the length ; disposed in longitudinal parallel rows, ten rows on a 

 branch, separated by strong longitudinal ridges, which are frequently granu- 

 lose : peristomes thin, scarcely elevated. Between each two adjacent aper- 

 tures, in the longitudinal direction, there is a prominent spiniform conical node. 



