290 



TRENTON FOSSILS. 



FIG. 187. 



FIG. 188. 



The vertical lamellae converge from the sides of the cell towards the center, but probably do not meet at 

 the center. They are unequal in number, varying from twenty to thirty ; are 

 often partially obliterated, and leave the inside of the tube marked only by 

 sharp ridges, corresponding to the stria3 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 the weathered 

 specimens. 



Fig. 187 represents a vertical section of a compact specimen of the Colum- 

 naria alveolata, showing the striated walls of the cells. 



This coral occurs in hemispherical masses, varying in diameter from three 

 inches to three feet, in Vermont. A specimen was discovered in New York 

 which originally must have weighed from 2000 to 3000 pounds. 



Escharopora (Hall.) The coral of this genus consists of a solid cylindrical 

 or subcylindrical stem, gradually tapering above, expanded and attached by 

 root-like ramifications below; surface entirely celluliferous ; mouths of cellules 



oval, scarcely contracted, inclosed in a rhomboidal space formed by elevated oblique lines, which cross the 

 coral in two directions; cellules consisting of oval tubes of nearly equal dimensions throughout, which 

 radiate in an ascending direction from an imaginary axis. 



Fig. 188 represents a part of Escharopora recta (Hall). The coral is straight, rigid, unbranched, cylin- 

 drical, or slightly compressed. It is found in Trenton limestone in Vermont, at Larrabee's 

 Point in Shoreham, and in South Hero. 



Stictopora (Hall.) This is foliaceous, somewhat calcareous, branching coral, attached 

 below by a smooth root-like expansion ; stems and branches bifurcating, and sometimes 

 coalescing, celluliferous on both sides, with a thin central axis; cellules consisting of oval 

 tubes, not urceolete or utricular; apertures distinctly oval, with a raised border nearly as 

 large as the cell within. 



Fig. 189 represents a small piece of rock covered with fragments of the Stictopora 

 ramosa (Hall.) It is said to occur in Trenton limestone at Larrabee's Point in Shoreham. 

 S. ramosa is a branching, erect, somewhat stony coral, covered on both sides by a 

 celluliferous crust; branches flattened; cells oval, in quincunx order; arranged in regular 

 oblique lines, alternating with each other in the direction of the axis, opening obliquely 

 upward and outward; mouths of the cells in perfect specimens elevated; more perfectly 

 rounded at the upper side. 



Stromatocerium rugosum (Hall.) This species of coral is exceedingly abundant 

 in the Black River limestone in Vermont. It is found in this limestone upon the island 

 in Button Bay, in Ferrisburgh, and at Isle La Motte. In Trenton limestone it has also 

 been found in South Hero. 



This coral is hemispherical; it increases in concentrated laminae or strata; the laminae 

 are numerous and wrinkled; and there are some faint indications of vertical tubes or 

 cells. It usually appears as a rough shapeless excrescence upon the 

 weathered surface of the limestone; and a little examination shows it 

 to be composed of concentric layers. 



Fig. 190 represents a specimen of Stromatocerium ruyosum of natural . 

 size. It exhibits distinctly the concentric lamination of the coral. The ft 

 coral, however, is often of much larger size than the one figured. 



Escharopora recta. Streptelasma (Hall.) This coral belongs to the family of cyatliophyl- 

 lidea. It is turbinate, gradually or abruptly expanding above; form like 



cyathophyttmn ; terminal cup more or less deep; lamellae vertical or longitudinal, more or less spirally 

 twisted together when meeting in the center. 



FIG. 189. 



