Coral lapideous, covering extraneous bodies, or in a simple mass, formed of concentric strata; strata composed each of a union of numerous alveoles, which are very short, contiguous, reticulate, and generally parallel.
Species.
A. glomeratus, alveoles vertical, subequal, oval, or obsoletely hexagonal, much shorter than the diameter, parallel; paries simple; strata numerous, forming a rounded mass. (Cabinet of the Academy of Natural Sciences.)
Found often on the coast of North America, cast up by the waves, the animals sometimes still living. Forms masses of various sizes and figures, generally more or less rounded or lobed, and composed of a great number of concentric layers. The number of these strata seems to be regulated in some degree, by the quantity of surface they have to cover. Thus if the nucleus happens to be a small shell, such as the Naticæ, Nassæ, &c. of our coast, or even the oyster, (O. virginica,) clam, (V. mercenaria,) &c. the strata are often very numerous; but on the thoracic plate of Limulus polyphemus, having a considerable space over which to extend themselves, the strata are but few, not more than 2 or 3. I have seen the thoracic plate of this animal so entirely covered by the Alveolite, as to have the eyes and stemmata concealed so as to be perfectly blind. When composed of a single layer only, it much resembles a Flustra, or a Cellapore of which the convex surfaces have been removed by attrition. The animal I have not yet examined. The alveoles or cells of a layer, are arranged in lines of different degrees of curvature, obscurely radiating from different centres; these lines are placed side by side, the alveoles alternating with each other throughout the layer in a quincunx manner; the thickness of the paries is somewhat equal to one half of the conjugate diameter of the alveole, the length of which, or thickness of the layer, is scarcely more considerable; but these proportions vary.
The species to which it seems allied, are madreporacea and incrustans. The former is fossil, and differs in being subramose; the latter forms but a single expansion.
Genus Favosites, Lam.
Coral lapideous, simple, of a variable form, composed of parallel prismatic and fasciculated tubes; tubes contiguous, pentagonal, or hexagonal, more or less angular, rarely articulated.
Species.
F. striata, more or less turbinate; paries of the alveoles longitudinally striated within, and fenestrate with minute osculi; alveoles with very numerous septæ. (Cabinet Acad. Nat. Sciences; and Peale's Museum—common.)
Found fossil in various parts of the United States, at the falls of the Ohio; Genessee, New-York; Pittsburg and Wilksbarre, Pennsylvania; Missouri, &c. &c. but not yet in the alluvial deposit of New-Jersey.