LONSDALE ON MIOCENE CORALS FROM N. AMERICA. 



507 



same side of the mouth. It was small and shallow, but open, the 

 edge being well defined and slightly thickened. The tubercle 

 beneath the mouth was also not constantly present, consisting 

 sometimes of a slight swelling of the porous surface, but more 

 generally of a small solid boss (b). 

 Locality. — Petersburg, Virginia. 



8. Cellepora umbilicata. (Sp. n.) 



Incrusting ; cells in successive enveloping layers ; shape irregularly oval or 

 pyriform ; surface bounded by a row of minute foramina, centre uneven, towards 

 the proximal extremity a large transverse foramen, near the mouth two smaller 

 foramina, in general more or less obliterated ; mouth transversely oval, slightly 

 inclined backwards, margin scarcely raised, not thickened, walls of cells separ- 

 able ; vertically fractured section irregularly columnar ; connecting foramina 

 near base of wall. 



a. Portion of Cellepora umbilica magnified four times in linear dimensions, 

 exhibiting near the edges cells in the earliest state or without the surface cover- 

 ing, and also the columnar chai-acter of the cells. 



b. Part greatly enlarged, to show the characters of the surface and the fora- 

 mina : it gives also exposed portions of the covering of inferior cells. 



In all the leading structural peculiarities this species agreed 

 with the last, except in the slightly inclined position of the mouth ; 

 and the generic assignment must be considered only provisional ; 

 in the minor details, the differences were considerable. The mode 

 of developing additional cells on a nearly uniform level was also 

 the same. No decided gemmuliferous chamber was noticed, but 

 beneath the proximal lip of the mouth a minute indentation was 

 frequently observed ; and in the same position, but chiefly in the 

 underlying layers, a prominent tubercle ; and where this structure 

 occurred, the two smaller foramina were situated at its base. The 

 indentation or tubercle agreed in situation with the chamber or 

 vesicle, armed, when perfect, with a long conical process in Celle- 

 pora pumicosa. In general only one row of pores surrounded 

 each outer covering, but occasionally there was an intermingling 

 of foramina, due apparently to defective developments. In the 

 underlying cells the mouth was often obliterated, and the central 

 foramen much contracted or filled up, but the boundary pores 

 generally remained open : there were, moreover, no clear in- 

 dications of external thickenings dependent upon age. 



Locality. — Petersburg. 



