264 



Still, in many of them the structure of the septa, pali, <fec., is- 

 easily made out. 



The wall is thin and covered by a sBiooth ejpitheca, having 

 wavy transverse lines and concentric folds. There are broad 

 costce corresponding to the first and second orders of septa, but 

 they are barely traceable beneath the epitheca.; the tertiaiy 

 septa have no costse corresponding to them. The intercostal 

 spaces are iisually marked by a double row of very fine pores, 

 due to the wearing of the epitheca. As this wears still fur- 

 ther the costse and the pores between them become very con- 

 spicuous, until finally, by its complete removaj, a skeleton of 

 the coral is left, showing twelve strong costse reaching from the 

 pointed base to the margin of the calice, where they axe con- 

 tinued as septa. Such skeleton coralla are very numerous at 

 the chief locality, Brown's Creek. 



Tlie dimensions of the type, which is a good representative 

 adult specimen, are : — Height of corallum. 17.5 mm. ; diameter 

 of calice, 4.5 mm. 



Locality, (&c. — Very abundant in Eocene strata at Brown's 

 Creek; less so at Hamilton Creek and Wilkinson's No. 4 sec- 

 tion, all of which are neighboring localities in the Cape Otway 

 district of Victoria. 



A comparison of this description of 0. velata with that of 

 C . laticosfata by Ten. Woods shows that the two species are 

 closely allied. The latter is more elliptical as to its calice as 

 well as in transverse sections of the corallum. Its costse also are 

 more prominent, while the crested ridge on the outer edge of 

 the curved corallum becomes a constant and distinctive feature. 



EXPLANATION OF PLATES. 



Plate V. 



Fig. 



1. Platytrochu? Airemis — a, corallum, 4 diam.; h, calice, 6 diam. 



2. Platytrochus hastatus — a, corallum, 4 diam. ; 6, calice of another 



example, 8 diam. 



3. Platytrochus curvatus — a, corallum, 4 diam. ; h, calice, 10 diam. 



4. Platytrochus vacuus — a, corallum, 6 diam.; />, calice, 8 diam. 



Plate VI. 



1. Conocyathus scrohiculatus — a, corallum, 6 diam.; h, calice, 12 diam. 



2. Ceratotrochus exilis — a, coralluni, 3 diam.; b, calice, 12 diam. 



3. Ceratotrochus Halli — a, corallum, 3*5 diam.; h, calice, 8 diam. 



4. Cyathosmilia velata — a, corallum, 2 diam.; b, calice, 6 diam. 



