2 PALEONTOLOGY OF NEW YORK. 



For some distance below the calix-margin the lamellae are of the same size, 

 their edges smooth and rounded, becoming sharp below, and their sides often 

 distinctly granulose or spinulose. The primary lamellae unite and coalesce 

 at the center of the calix, forming an indistinct plate or vesiculose core from 

 3 to 5 mm. in diameter. Fossette obscure or obsolete. 



This species is distinguished by the usually rigid straightness of its form, 

 and the .strongly ribbed exterior. 



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

 group, at Catskill creek, Greene county; near Clarksville; at Schoharie and at 

 numerous other localities in the State of New York. 



ZAPHRENTIS, Rafinesque. 1820. 

 Zaphrentis Roemeri. 



PLATE I, FIGS. 11-21. 



ZaphretitU Rnetneri, Edwabds & Haimb. Monog. des Polypiers Fossiles, Paris, 1851. 



Report of State Geolog-ist for 1882. Expl. pi. 1, figs. 11-21. 

 1883. 



CoRALLOM simple, turbinate, regularly or irregularly curved; acute at base. 

 The exterior often sharply and strongly annulated, with numerous fine con- 

 centric striae, and constrictions caused by intermittent growth ; radial costae 

 very distinct ; base acute. 



Calix very oblique to the axis of the corallum, sides sloping, bottom broad, 

 marginally depressed, flat or slightly concave at the centre. Fossette com- 

 mencing at varying distances from the center of the calix, at first forming a 

 deep pit, becoming shallower <as it approaches the anterior margin. Lamellae 

 from eighty to ninety, alternating in size, the smaller ones being merely 

 rudimentary. 



The extension of the lamellae toward the center is subject to great varia- 

 tion ; in some specimens the greater part of the tabula remains smooth, the 

 lamellae extending but a short distance from the margin ; in other specimens 

 extending to and becoming irregularly involved at the center. Tabulae thin 

 and very closely arranged. 



