136 PALiEONTOLOGY OF NEW-YOBK. 



523. 1. STROMATOPORA CONCENTRIC A. 



PL. XXXVII. Figs. 1 a -/. 

 Compare S. concentrica, Goldfuss, Petrefacta, pag'. 22, pi. viii, fig. 5, 1826. 



— — Dk Bi.Ai.\viLLE, Man. d'Actiiiologie, pag 413, pi. 70, fig. 1, 1834. 



— — Lonsdale : Murchison, Silurian System, pag. 680, pi. 15, fig. 31, 



1839. 



Coral hemispheric, spheroidal or irregular in form, composed of thin concentric laminaj 

 which arc visible in weathercil specimens ; an apparent fibrous structure often visible in a di- 

 rection vertical to the larain;e ; surface of the lamina; marked by minute pores not contiguous. 



The structure abov'e indicated is all that can be seen by the naked eye, or even with a good 

 magnifier ; but in specimens fovorably weathered, the fibrous structure, when much magnified, 

 is seen to be composed of cylindrical tubes penetrating the lamina;. These laminae are scarcely 

 so tliick as writing paper, and sometimes the ends of the tubes may be seen penetrating them, 

 and showing the spaces between which appear to be quite solid. 



This coral is Extremely abundant, but attracts little attention from its apparently amorphous 

 character ; but it is nevertheless very interesting, and although composed of such minute cells, 

 and increasmg by such exceedingly thin layers, it forms masses of one and two feet in diameter, 

 larger even than any individuals of Catenipora, Heliolites or Favosites in the same rock. 

 The extremely minute structure renders it impossible to point out specific distinctions, if any 

 exist, between this coral and a similar one in the coralline limestone ; though it is possible 

 that specimens more favorably weathered than any I have yet seen, may indicate some slight 

 difference of character. In the general aspect, mode of weathering, and color of the mass, 

 there is a veiy striking similarity between those just noticed and the species in the Delthyris 

 shaly limestone, Avhich proves, however, quite distinct. It cannot for one moment be doubted, 

 that the numerous large and small masses of this coral seen at Lockport are organic in their 

 structure. 



Fig. 1 a. The surface of a small hemispheric mass, showing the edges of the thin laminaa 



which are unequally weathered. 

 Fig. 1 i. A magnified portion of the same surface, showing the circular ends of the cylindrical 



tubes. 

 Fig. 1 c. A magnified portion, showing the weathered edges of successive laminaB which are 



indented by the cells, giving them the appearance of being arranged in concentric 



lines. 

 Fig. 1 d. A transverse section of a small mass. 

 Fig. 1 e. A magnified portion of the same. 



Fig. 1/. A larger mass, showing the efl^ects of weathering upon the thin concentric laminae. 

 Fig. 1 g. The base of the same specimen, showing several centres of growth. 



Position and locality. In the lower part of the Niagara limestone : very abundant at Lock- 

 port, and less common in Orleans county and at Rochester. 



