472 



BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



" This .species is found throughout the great Marl formation, and 

 presents every variety of siliceous fossilization, from that charac- 

 terized by silicification of the sclerenchyma and infiltration of the 

 interspaces by granular carbonate of lime, to that where all is siliceous 

 and capable of polish. Destructive silicification almost invariably 

 exists in a greater or less degree; and as the sections preserved were 

 made, as a rule, for ornament or amusement, I have seldom seen 

 accurately transverse and longitudinal views of the corallites. 



"All the specimens, with the specific peculiarities mentioned, may 

 be ranged in several groups; that which contains the detailed char- 

 acters in their greatest intensity, generally, may be considered the 

 typical form. 



"a. Astraea crassolamellata, typical form. 



"Corallum large, irregularly convex above. Corallites tall, large, 

 crowded here and there, but not so much so higher up or at the sur- 

 face. Calices circular, but more or less elliptical when on an irregularity 

 of the surface; very large, and separated from each other by well- 

 marked, furrow-shaped, polygonal tracts; tracts marked by costal 

 elevations and by granules. 1 Calices crateriform, not much elevated 

 above the surface. Wall thin, and rendered insignificant by the 

 great development of the septa at the margin. Fossa not deep. 

 Costae numerous, and, considering the diameter of the septa at the 

 wall, very small; they project but little, and are, as a rule, alter- 

 nately large and small, not dentate, and often incline one to the other 

 at their free edge. The larger costae present regular enlargements 

 where the cross-tissue (dissepiments) of the exotheca joins them, 

 when there are more than four cylces of septa, the smaller costae 

 are irregular as regards their appearance and development. Colu- 

 mella large, of lax laminae, parietal; it does not project much at the 

 bottom of the fossa, and occupies a large space in the corallite. 

 Septa numerous, generally characterized by great enlargement at the 

 wall, and linear appearance in the rest of their course, the higher 

 orders being nearly linear at the wall also. The number of cycles 

 varies with the stage of development of the corallite. 



Analysis of the species. 



Intercalicnlar 

 furrow. 



Septa. 



Cycles. 



Diameter of 

 corallites. 



a. Astraea 



(type). 

 6. var. 



crassolamellata 



Well marked. . . 



-var. 

 -var. 

 -var. 

 - var. 

 -var. 



magnetica. 

 pulchella.. 



nobilis 



minor 



nugenti... 

 magwifica. 



do 



Less well marked 



do 



do 



Less marked . . 

 Well marked. . 



Verv thick at wall . 



do 



do 



Very large at wall . . . 

 Very thick at wall . . 



do 



Less thick, more 

 linear. 



4, in some 5. 



Variable . 



do... 



2 and 3. . 



do.. 



4to6.... 



19 to 20 mm. 



12.7 mm. 

 8 to 12.7 mm. 

 Variable. 

 Small, variable. 



Do. 

 8 to 25 mm. and 

 more. 



i As none of the specimens exhibit, perfect calices many of these characters have, of necessity, been taken 

 from casts. 



