120 



PALAEONTOLOGY OF NEW-VORK. 



Genus ASTROCERIUM {nov. gen.). 

 [Gr. adTTip, Stella, and XT;piov, fams ; in allusion to its similarity to Favosites with stellate cells.] 



Coral massive (or ramose?) ; interior prismatic or basaltif'orm ; cells contiguoiL":, openings 

 upon the surface more or less angular, and often Tery variable in size ; rays twelve or more, 

 consisting of slender elongated and ascending points ; transverse septa direct. 



In some species, the columns or cells are contracted at intervals during the process of growth. 



The corals of this genus resemble Favistella ; but I have separated them, on account of 

 the spiniform rays which constitute a marked distinction, those of the latter genus having con- 

 tinuous lamclliform rays. Making this distinction, we shall find the genus Favistella, if not 

 confined to lower Silurian strata, at least more decidedly typical of ihat period*. 



The form and general character of the species of this genus is like that of Favosites ; and 

 in many specimens the absence of the slender spiniform rays leaves the transverse septa alone, 

 making it nearly impossible to distinguish them from Favosites. 



511. 1. ASTROCERIUM VENUSTUM («.*;).). 



Pl. XXXIV. Fig. lo-i. 

 Forites ? Rep. 4th Geol. District, pag. 86 and 91, figs. 25 and 27. 



Corallum hemispheric or spheroidal, massive, commencing growth upon other bodies ; com- 

 posed of small angular tubes or cells, which increase by lateral and interstitial additions ; 

 interior of cells stellate, with twelve ascending spiniform rays ; septate transversly ; openings 

 on the surface stellate, or solid and columnar. 



This species occurs in masses of greater or less dimensions, often reaching two or three feet 

 in diameter, and sometimes even larger. In its general aspect, it is composed of stellate tubes 

 of from j'j to ^V of an inch in diameter. The rays are composed of slender spines rising from 

 the side of the tubes, and pointing upward ; and between each series of these there is a trans- 

 verse septum. Specimens, however, are usually so imperfect that a longitudinal section pre- 

 sents a confused septate and radiate character. In some specimens the transverse septa alone 

 are preserved, with the bases of the spines upon the sides of the tube. In other cases the rays 

 alone are preserved with few of the septa, so that the strict application of characters is liable 

 to difficulty. The solid specimens present the columnar character of Favosites, from which 

 they are not readily distinguished, but the ends of the tubes are still stellate in many of the 

 solid masses. 



One peculiarity of this species is that of being marked at intervals by strong laminse parallel 

 to the surface, and indicating periods of growth. The entire substance of the coral is some- 



* The species of Favistella described under the Clinton group may perhaps belong to the genus now constituted, 

 or form a connecting link between the true Favistella of the lower siluiian period and those now described. In 

 many instances where the ends of the tubes appear stellate in solid specimens, it is not easy to discover whether they 

 arc spiniform or lamiUiform rays; sections of snrli specimens do not always reveal the true structure. 



