158 



PALJEONTOLOGY OF NEW-YOR«. 



552. 1. DIAMESOPORA* DICHOTOMA (n. sp.). 



PL. XL B. Fig. 3o-d. 



Coral occurring in regularly bifurcating cylindrical stems, which usually consist of a thin 

 envelope or membranous crust enclosing inorganic matter ; interior surface of hollow stems 

 striated transversely ; cells opening upward, and arranged in regular ascending or spiral lines ; 

 calicles prominent, nariforra. 



This species sometimes approaches Trematopora ostiolata in its appearances ; but the very 

 conspicuous nariform calicle, where not worn off, at once distinguishes it. The stems are usually 

 flattened, and its regular bifurcation likewise distinguishes it from Trematopora. In some 

 instances where the stem is flattened and worn, elevated lines or ridges are visible between the 

 rows of cells, and it approaches in appearance to the surface of Escharopora, and, in its 

 totality of characters, it appears to form a link between that genus and Stictopora. 



This species is usually associated with Stictopora and Trematopora ; and in small frag- 

 ments the stems retain their cylindrical form, and are rarely solid throughout, though there is 

 no evidence that the cells reach to the centre of the stem. In the strong stems just below the 

 point of bifurcation, thirty-five or forty cells may be counted in the circumference, and about 

 twenty in the circumference of each branch above. 



Fig. 3 a. A fragment of a stem bifurcating above and longitudinally divided below, showing the 



striated interior. 

 Fig. 3 b. The surface enlarged, showing the form and arrangement of apertures. 

 Fig. 3 c. An enlarged portion where the ridges betweea rows of cells are conspicuous. 

 Fig. 3 d. A fragment of a stem preserving a cylindrical form, and commencing to bifurcate above. 



In the transverse sections of the two branches, one is solid while the other is hollow. 



Position and locality. On the surface of calcareous layers in the shale at Lockport. 



' This generic name is introduced in this place as indicative of the character of this coral ; but since no other species 

 have fallen under observation, the generic description is reserved for the result of further investigations. 



