DESCRIPTIONS OF SPECIES. 79 



septal mass, reinforce the columella. Passing outward, the trabeculse bend 

 more and more from the columella. The septal margins are crenate. There 

 are processes extending inward from the wall similar to those seen in Trocho- 

 cyatlms lunuUtiformis and T. depressus. Synapticulaj (pseudo) are sometimes 

 present near the places of fusion of the higher to the lower cycles of septa. 

 Where the septa come very close together the lateral granules sometimes 

 fuse across the interseptal loculi. 



DiscOTROCHUS OBBiGNiANUs Miliie-Edwards and Haime. 

 PI. V, figs. 13 to 19b. 



1848. Discotroclms orbigniamis Milne-Edwards and Haime. Annales sci. nat., 3d ser.. 



Vol. IX, p. 252, pi. vii, fig. 6. 

 1851. Discotrochus orbignianus Milne-Edwards and Haime. Polyp, foss. des Terr. 



Pal., p. 30. 

 1857. IHscotrochus orbignianus Milne-Edwards and Haime. Hist. Nat. des Corall., 



Vol. II, p. 76. 

 1861. Bisvotrovhus orbignianus de Fromentel. Introd. a I'fitude des Polyp.foss., p. 93. 

 1881. Biscotrochus orbignianus Queustedt. Kiihren- und Sternkorallen, p. 948, pi. 



clxxix, flg. 95. 



1895. Biscotrochns orbignianus Vaugban. Am. Geol., Vol. XV, p. 213. 



1896. Biscotrochus orbignianus Vauglian. Bull. U. S. Geol. Survey No. 142, p. 48. 



The following is a translation of the original description : 

 Corallum very flat; lower surface concave in its central portion, horizontal near 

 the edges. Costa- unequal, rather large, slightly prominent, indistinct in the central 

 part, which is separated from the flat marginal portion by a small circular rim. Calice 

 somewhat flat, or very slightly convex, with fossa scarcely indicated. Columella 

 moderately developed. Five orders of septa; six equal systems. Septa unequal, 

 slightly elevated, regularly convex above, moderately thin, crowded together; those of 

 the fourth and fifth orders larger than the tertiaries. The faces covered with very 

 large grains, almost equally spaced, but disposed in series sensibly vertical. Height, 

 1.5 mm. ; diameter, 6 mm. Fossil from Alabama. Collection Alcide d'Orbigny. 



This description is so excellent that I do not change it. 



The young individuals of this species present certain peculiarities 

 worthy of note. A series of young specimens are represented in PI. V, 

 fio-s. 14 to 16a. The youngest specimens that I have are disk-like, or, 

 differently expressed, resemble a section of a small cylinder. The specimen 

 shown in PI. V, fig. 14, is 4.5 mm. in diameter and about 1 mm. high. 

 It has an almost perpendicular wall and shows no sign of attachment. In 

 the next stage the costse around the base begin to project beyond the 

 perpendicular wall and to form with the septa an arch extending thi-ough 



