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 
oT the preceding species. Externally the tubes, like those of the other species, are striated, or 
fluted, the strke corresponding to the number of fays or lamelke. 
Fig. 2 a. A transverse section, natural size ; the rays for the most part obliterated. 
Fig. 2 b. 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 Milwaukee, 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 laminee are contiguous and pro¬ 
duce a solid coral*. 
*For further illustration, see Corals of the Delthyris shaly limestone. 
