140 EOCENE AND LOWER OLIGOCENE CORAL FAUNAS. 



plication is by fission or by septal budding. There are usually about three 

 cycles of septa, the first and second cycles being of the same size. They 

 are strong, and their sides are beset with small granules. Endothecal dissepi- 

 ments exist. Usually they are rather thin, curve uj)ward and out, and are 

 about 1.5 mm. apart. The calices when viewed from above show a lamellar 

 columella, but in sections it appears as either lamellar or trabecnlar, or 

 there may be only a calcareous deposit around the inner ends of the 

 septa. In the sections the lamellar columella does not appear to be a 

 separate structure, but only a jirolongation of one of the principal septa, as 

 one of the corallites in the magnified cross section (PI. XV, fig. 4b) shows. 

 Sections of other corallites show the same feature very clearly. 

 Locality. — Prairie Creek, Alabama 



Geologic occurrence. Midway bcds. 



Type. — United States National Museum. 



Remarks on Dichocoenia alabamensis and D. stokesi M.-Edw. and H. As UO SpCCimCUS of 



Bichocoenia porcafa (Lamarck), the type species of the genus, ^ were available 

 for comparative study, comparison Avith T). stokesi M.-Edw. and H. was insti- 

 tuted. Excellent material of this species is in the United States National 

 Museum and in my own private collection, through a contribution from Mr. 

 R. T. Hill. The general dspect of the corallum, type of wall (a pseudotheca), 

 and character of columella in D. alabamensis, coiTespond exactly to those of 

 D. stokesi. The septal margins in the type of the former species are broken 

 away; therefore to ascertain whether the two were really generically 

 identical a miscroscopic examination of the septa of two species was made. 

 The septal structure of D. stokesi will be described, arid then i). ala- 

 hamensis will be compared with it. The septa in the former species are exsert, 

 and are composed of ascending trabeculfp, with a line of divergence coin- 

 ciding with the vertical axis of the septal arch. The trabeeulre pass U2:)ward 

 and inward on the inside of the line of divergence, and iip ward and outward 

 on the outside of the same line. The courses of the trabecular are indicated 

 on the septal faces by elevated stria; or by fine rows of small granules. The 

 septal margins are not entire, but are finely dentate. The dentations are 

 small, but are distinct, and usually quite sharp on the exsert portion. Tlie 

 margin of the inner free portion may have })ointed dentations, or fine crena- 

 tions. Microscopically the pali exhibit no special difference from the septa, 

 except they seem to possess a line of divergence independent of that of the 



'Milne-Edwards aud Haime, Mon. Brit. Foas. Corals, Pala-outogr. Soc, p. xsx. 



