NIAGARA GROUP. 



141 



Fig. 2 a. A fragment of a frond having the cells filled and solid, separating in prismatic forms. 

 Fig. 2 J. A portion enlarged, showing the structure. 



Position and locality. In the lower part of the Niagara limestone at Lockporl. 

 530. 7. CLADOPORA RETICULATA {n. sp.). 



PL. XXXIX. Fig. 3a- e. 



Coral expanded into a broad reticulate frond ; branches roundish or slightly flattened, coa- 

 lescing at frequent intervals, and forming meshes of various form and size, poriferous on all 

 sides ; openings of the cells upon the surface roundish or oval, distant from each other rather 

 more than their diameter, often arranged in parallel longitudinal lines ; interior showing the 

 cells reaching to the centre from all sides, and, in solid specimens, becoming prismatic. Cells 

 distant from each other ■g\ of an inch. 



This species has the general aspect of a Retepora, but a slight examination proves it pori- 

 ferous on all sides, having round tubular cells, which, in perfect specimens, open upon the 

 surface by nearly circular mouths, having a projecting lip on the lower side. In slightly worn 

 branches, the openings are quite circular ; and in those more worn, they become somewhat 

 angular. From unequal wearing, the openings sometimes appear oval ; and from other causes, 

 specimens often present a variety of appearance. The spaces between the mouths of the cells are 

 slightly gi-eater than the width of the openings themselves, and, in longitudinal sections, this is 

 distinctly seen penetrating to the axis, while the cell appears like a gradually enlarging tube 

 from the centre to the surface of the branch. In specimens wholly crystalline, it is impossible 

 to distinguish any thing beyond a general prismatic or fibrous structure. 



Fig. 3 a. A part of a large frond, showing the branches and reticulations of the natural size. The 

 branches, in their circumference, have seven distinct rows of pores, arranged in 

 nearly regular longitudinal rows. 



Fig. 3 b. An enlarged portion, showing the form and arrangement of the cells upon the surface. 



Fig. 3 c. A similar enlargement where the surface is worn. 



Fig. 3 d. A longitudinal section enlarged, showing the interior arrangement of the tubular cells. 



Fi.g 3 e. A fragment of another frond having only six longitudinal rows of pores on the branches, 

 which gives a greater lateral distance between the openings on the surface, though 

 presenting no appreciable difference in the longitudinal distance. In other respects 

 this specimen preserves all the characters of the preceding one, and of others of the 

 same species. 



Position and locality. The specimens figured were found, associated with Catenipora escha- 

 roides, near Louisville, Kentucky. I have found small fragments of the same or a very similar 

 species at Lockport ; but the evidence of the geological position of the specimens figured rests 

 chiefly on their association with Catenipora, and that the limestone containing both is below 

 the limestone containing the fossils identical with those of the Onondaga and Corniferous lime- 

 stones of New-York. 



