BLACK-RIVER LIMESTONE. 
47 
CORALS OF THE BIRDSEYE AND BLACK-RIVER LIMESTONES. 
Plate XII. 
80. 1. COLUMNARIA ALVEOLATA. 
Pl. XII. Figs. 1 a, b, c. 
Columnaria alveolata. Goldfuss, Petrefacta, pag. 72, tab. xxiv. fig. 7 a, b, c. 
— — Eaton, Geol. Text-Book, pag. 131, pi. 4. 
Columnaria. Emmons, Geol. Report, pag. 276, fig. 2. 
A hemispherical or irregularly massive coral, consisting of radiating, parallel or diverging 
tubes ; tubes hexagonal (or varying from 5- to 7-sided ), striated longitudinally, crossed by 
transverse dissepiments with vertical radiating lamellae ; no communicating pores. 
The vertical lamellae converge from the sides of the cell towards the centre, but I have 
not yet seen a specimen in which they meet at the centre. These lamellae are unequal in 
number, varying apparently from twenty to thirty, and never meeting in the centre in our 
specimens : they are often partially obliterated, and leave the inside of the tube marked 
only by sharp ridges, corresponding to the striae upon the outside ; when the transverse 
dissepiments are also obliterated, these ridges are denticulated, marking the point of 
junction. The vertical lamellae are only visible in weathered specimens, as fig. 1 b , where 
the ends of the tubes are exposed. In a large number of specimens, the radiating lamellae 
are entirely obliterated, and the dissepiments only preserved, as in fig. 1 a. These are 
common at Watertown, Jefferson county. In the Mohawk valley and elsewhere, when 
preserved in compact limestone, the tubes are solid, separable from each other, r.nd 
preserving very perfectly their deeply striated surfaces, as in fig. 1. 
The coral occurs in hemispherical masses, t arying in diameter from three inches to 
several feet.* 
Fig. 1. A vertical section of a compact specimen, showing the striated walls of the cells. 
Fig. 1 a. A vertical section, showing the transverse dissepiments, with the vertical lamellce obliterated. 
Fig. 1 b. A transverse section (weathered surface), showing the radiating lamellae. 
Fig. 1 c. The same enlarged. 
Position and locality. Glensfalls ; Chazy ; Watertown ; Lowville, Lewis county ; Am¬ 
sterdam and numerous other places in the Mohawk valley, always confined to the Black-., 
river limestone, and is never known to rise above it in any locality. In many situations, it 
forms a large portion of a single thick stratum near the termination of the rock. 
* There is a specimen (a portion only of an entire mass) in the State Collection, weighing about 1500 pounds : the 
whole mass probably weighed 2000 or 3000 pounds. This specimen is from the Mohawk valley, and was blasted from 
tire rock in quarrying stone for the enlarged Erie Canal; and I am indebted to the Engineer, Mr. M'Alpin, for being 
able to place it in the Collection. Certainly, when we find at so early a period such masses of coral, there is no reason 
why extensive coral reefs may not have margined our early shoals or islands of granite, as those of modern origin do 
the islands and shoals of our present seas. 
