Say on Shells, 4^c. 385 



in miniature, basaltic columns ; when the alveoles are free on 

 the surface, these fossils are known by the name of petrified 

 wasp-nests, from the resemblance they bear to the nests of 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 rolled 

 pebbles of the Delaware River, near Philadelphia, are com- 

 pletely silicified. 



The size varies from one fourth of an ounce, to two 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 less turbinate, but are some- 

 times depressed or compressed, and the tubes rectilinear or 

 excurved, and of various lengths. The dilated summit is not 

 90 much the eflfect 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 septae, 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 prominent, 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- 

 veolata. Lam.) in not being "extus transverse sulcata." It 

 seems to be allied to Corallium Goihlandicum, Amcen. Acad. 

 V. 1. p. 106, and it is possible it may prove synonymous, or 

 very similar to it, when that species becomes better known ; 



