TRENTON LIMESTONE. 
65 
of Favosites Ly coper don* Some of the hemispherical masses show a great divergence of the 
tubes, as if radiating from an axis ; while others are nearly vertical. Specimens approaching 
a conical or ramose form exhibit a tendency to radiation of the tubes from a central axis. 
A comparison of all these forms shows no essential difference of structure, farther than 
might be expected from the different conditions under which the fossil was developed ; and 
I am at present disposed to regard all the forms referred to this species as varieties of the 
same, although there may be some links wanting to show the perfect gradation from the 
hemispheric to the ramose forms. It is not intended to be understood that the hemispheric 
and globular masses always develop the ramose varieties, like fig. 2, pi. 23 ; these doubt¬ 
less having this form from their commencement. Still the specimens 1 g, pi. 23, and 1, 
pi. 24, show that the massive varieties do sometimes become ramose to some extent; and 
there are other specimens, which could not be represented in figures, that prove more 
clearly the development of the ramose, from the massive forms. In addition to these more 
regular forms, this coral sometimes presents itself in irregular massive forms, as if, while 
a group had been growing, they were disturbed, a part of the polyps being destroyed, and 
the others growing onward and increasing, finally producing shapeless masses. 
These remarks are made for the purpose of calling the attention of the student to these 
circumstances, particularly as the hemispheric masses alone have been referred to Say’s 
species. These observations will be better understood by a comparison with the following 
figures, drawn from different specimens. 
.Fig. 1. Portion of a vertical section of a hemispherical form of large size, showing the radiating 
structure from increase of tubes by subdivision, and also the increase by development of 
marginal tubes. The tubes are filled, and have become solid columns, which are easily 
separable by a slight blow of the hammer. 
Fig. 1 a. A portion magnified, showing only the enlarged columns; the diaphragms not visible. 
Fig. 1 b. Transverse section of a small conical or hemispheric form, showing the radiating arrangement 
of the tubes. 
Fig. 1 c. A portion of the same enlarged, showing the diaphragms at regular intervals in some of the 
tubes which are divided longitudinally. 
Figs. 1 d, e, f. Different external forms of the coral : 1 d and /J with more depressed forms, being the 
more usual; while 1 e shows a tendency to branching, which, if continued, would produce 
a coral with a massive centre and numerous branches. 
Fig. 1 g. A large irregular mass with numerous diverging branches, some of which are broken off, 
showing the radiating arrangement of the tubes from a central axis This specimen exhibits 
the same tendency as in 1 e, carried forward to a greater extent, showing how the same 
form may produce the ramose varieties. The tubes or solid columns, where the branches 
are broken off, present precisely the same structure as in the smaller hemispheric masses. 
Fig. 1 A A fragment from a larger mass, where the tubes are not filled with calcareous matter, showing 
the regularity of the diaphragms, which are distant a little less than the width of the tubes. 
Fig. 1 i. The same enlarged. The mass is light and spongy like recent coral, and appears to be com¬ 
posed of numerous smaller ones which were drifted together, and afterwards recommenced 
their growth, forming a very irregular mass. 
* From its resemblance to Ly coper don bovista. 
9 
[ Paleontology.] 
