NIAGARA GROUP. 



135 



522. 4. HELIOLITES MACROSTYLUS (n. sp.). 



PL. XXXVI A. Fig. 2 a, b, c. 



Tubes large, closely arranged ; rays strong ; interspaces apparently tubular. 



The single specimen of this species examined, differs from the preceding mainly in the size of 

 the tubes, which are comparatively closely arranged, and much stronger than in any specimens 

 of the preceding species. Externally the tubes, like those of the other species, are striated or 

 fluted, the striae corresponding to the number of rays or lamellae. 



Fig. 2 (Z. A transverse section, natural size ; the rays for the most part obliterated. 



Fig. 2 5. A part of the same enlarged. 



Fig. 2 c. A vertical section, showing the striated surfaces and close arrangment of the tubes. 



Position and locality. In the Niagara limestone at Milwaukie, associated with the preceding 

 species. (^Collection of I. A. Lapham.) 



Genus STROMATOPORA (Goldfuss). 



The characters of this genus, as given by Goldfuss, are not entirely satisfactory ; and 

 Blainville, after an examination of the specimen described by that author, expresses doubts 

 whether it be a true coral, while Ehrenberg supposes it may be a species of Porites allied 

 to one which he has named P. stromatopora. 



In the specimens here referred to this genus, there is so much general similarity to those 

 figured by Goldfuss and Lonsdale, and also an apparent identity with a specimen from Dud- 

 ley marked S. concentrica, that I cannot hesitate to refer this coral to the genus. Having a 

 similar species from the Delthyris shaly limestone, where the characters of the genus are better 

 developed, it appears that the coral is composed of minute cylindrical tubes with considerable 

 space between ; and that the laminated structure arises from thin layers of calcareous matter 

 deposited and filling the spaces between, and enclosing the tubes. In no examples have I found 

 the openings of the cells disposed in concentric lines or furrows. This tubular structure is not so 

 clearly visible, though still perceptible, in the Niagara species. Admitting the reference to the 

 genus, it appears from this structure to be more nearly related to Tubipora than to any other 

 genus, and differs from it in this, that the parallel connecting laminae are contiguous and pro- 

 duce a solid coral*. 



*For further illustration, see Corals of the Delthyris shaly limestone. 



