FAMILIES AlfD GENERA OF THE MADREPOBAEIA. 151 



with a flat or slightly concave base, and a convex calice with a 

 circular or oval fossa. Columella absent. Septa very numerous, 

 close, thin, unequal, uniting, crested, denticulate or moniliform at 

 the free edge, granular at the sides, imperforate. Synapticula 

 numerous. Dissepiments wanting. Epitheca of base in concen- 

 tric folds, stout or thin. 



Distribution. — Fossil. Eocene : Sind. 



The genus differs from Oyclolites, as amended by Pratz, in 

 having imperforate septa and no dissepiments. The species are 

 described in the "Eossil Corals and Alcyonaria of Sind," Pal. 

 Indica, Ser. xiv., 1880. The Erench Eocene Oyclolites probably 

 belong here. 



G-enus Bathtactis, Moseley, Beport on Corals, ^Challenger ' 

 Voyage, p. 185, pi. xi. (1881). 



Syn. Montlivaltia, Tennison "Woods ; Fungia, Pourtales, non 

 Dana. 



Corallum free, discoid, not attached or cup-shaped in the 

 young condition, thin and fragile. Primary septa free, the 

 others united so as to form six deltoid continuations. Upper 

 margins of septa usually coalescent over the apices of the deltas. 

 Septa deeply toothed. Synapticula sometimes abundant, some- 

 times few, arranged in a series of concentric circles. Columella 

 well developed. Base costulate. No epitheca. 



Distrihutioti. — Recent. Deep water, from 30 fathoms to 

 3 miles, North and South Atlantic, Caribbean Sea, South-Indian 

 Ocean, Malay Archipelago, West and East Pacific, Australian 

 seas. 



The specimens show that the columella is often reduced to the 

 junction of septa only. 



Moseley makes some most valuable remarks on the influence 

 of growth and nutrition on the species of BatJiyactis : — " In 

 some specimens, dredged on a siliceous bottom composed of 

 Diatom skeletons, the wall is excessively thin, and towards its 

 marginal region is perforated by a series of apertures on either 

 side of the costse." " When a specimen hardened in spirit is de- 

 calcified, the wall of the corallum in dissolving in the acid becomes 

 perforated by a similar series of apertures, yielding first at these 

 spots." 



