Say on Shells, &. 385 
in a basaltic columns; when the alveoles are free on 
the surface, these fossils are known by the name of pe 
wasp-nests, from the resemblance they bear to the nests = those 
insects. The silex is usually only infiltrated into the cavities, . . 
leaving the substance of the coral’ in its original calcareous 
state, but the specimens which are found amongst the roHed 
pebbles of the Delaware River, near Philadelphia, are com- 
pletely silicified. 
The size varies from one fourth of an ounce, to swo hun- 
dred pounds or more, and the tubes occur of every interme- 
diate diameter, from the fortieth to one fourth of an inch.’ It 
is not common to find any two specimens of like form, they 
are, however, ordinarily more or soi tarbinate, oe are some- 
times depressed or compressed, _ tubes 
excurved, and of various lengths. ‘The dilated summit is not 
-So much the effect of a gradual enlargement of the tubes, as 
of the frequent and adventitious interposition of young ones, 
which of course renders the openings of the tubes unequal. 
The tubes or alveoles, vary in the same coral, being 5 or 6, 
rarely seven sided, but the hexagonal form is most common ; 
the interior of a tube is divided into a great number of apart- 
ments or cells, by approximate transverse septe, each of the 
cells appears to be connected with the corresponding cells of 
the surrounding tubes, by lateral orifices in the dividing paries ; 
these orifices are minute, inequidistant, orbicular, their margins 
slightly promfaent; and forming from one to three longitudinal 
series on each side of the tube; each row is separated from 
the adjoining one by an impressed line. By means of these 
osculi it seems probable that all the animals inhabiting a com- 
mon coral, were connected together, or had free communica- 
tion with each other, but whether by means of a common or- 
gan as. in Pyrosoma, Stephanomia, &c. or simply by contact as in 
the aggregating Salpa, &c. we have no means of determining. 
The striata differs from Madrepora truncata, Esper. (F. al- 
yeolata, Lam.) in not being ‘extus transyersé sulcata.” It 
seems to be allied to Coralliwn Gothlandicum, Ameen, Acad. 
¥.1. p. 106, and it is possible it may prove synonymous, or 
very similar to it, when that species hecomes better known ; 
