128 



paljeontologt of new-yokk. 



Fig. 1 fl. A portion of a hemispheric specimen, giving the usual characters of the species as it 

 occurs in New-York. 



Fig. 1 b. The base of the same specimen, sho \ ing its mole of growth from below, and the in- 

 crease by interstitial cells, which appears like a bifurcation of a single tube. 



Fig. 1 c. A fragment from a strong growing mass, preserving the transverse striic, and showing 

 tubes somewhat larger than the preceding figure. 



Fig. 1 d. An individual where the growth is more slender, and the reticulate spaces are smaller. 



Eig. 1 c. A vertical section of the same, contrasting vv^ith fig. 1 c. 



Fig. 1 /. A vertical section of fig. 1 c, showing the transverse septa of the tubes, and also a eon- 

 fused cellular structure, which is probably due to crystallization, from the infiltra- 

 tion of siliceous matter into the interior. 



Fig. 1 g. A vertical section of a well preserved specimen, showing the external striated character 

 of the tubes, when magnified. 



Fig. 1 k. A longitudinal section of the interior of several tubes magnified, showing the strite. 



Fig. 1 i. A figure showing the vertical section of a mass of this coral, where the spaces are filled, 

 and the whole intimately combined with the surrounding stone. It is impossible, in 

 such specimens, to distinguish any characters of structure. 



The specimens 1 a, b, c, are from New- York, and show a stronger and more vigorous 

 growth than the specimens d and e, which are from western localities. Indeed the variation 

 sometimes appears sufficient for the establishment of a distinct species ; but as the specimens 

 present among themselves considerable variety, it is difficult to find constant characters. In all 

 the New-York specimens examined, the cells are round-oval, rather closely united, and the 

 coral of strong growth. In the western specimens, the openings of the cells are smaller, more 

 elongated, and not so closely united, and the coral more slender and delicate. The space of 

 one fourth of an inch covers the openings of two to three cells of the New-York specimens 

 while there are three to four in the same space in western specimens, although the latter are 

 less closely united. In other respects there appears no important difl'ereiice, though, from the 

 silicified condition of most of the specimens, the minute structure is rarely preserved in per- 

 fection. 



Position and localities. This coral has been already noticed under the Clinton group, in 

 which position it makes its earliest appearance. In the Niagara group, it occurs in almost every 

 locality in the upper part of the limestone ; but the condition of the rock is such that it is 

 frequently nearly obliterated, and it often requires careful examination to detect its remains 

 even where it has been abujidant. Nearly all the well preserved specimens are silicified, and these 

 remain while the surrounding rock is destroyed. In this condition the coral is more abundant 

 in the vicinity of Rochester and Brighton, Monroe county, than in any other localities. It is 

 less abundant in Wayne and Orleans counties ; and at Lockport are occasionally found frag- 

 ments of large masses, the principal portion entirely obliterated, and replaced by gypsum, 

 strontian, or other crystalline matter. 



