257 



ratio of 3 to 2. Septa exsert, highly granular, and in six" 

 unequal systems, the central ones being smaller than those at 

 the ends. The former contain three cycles of septa only, 

 while in the latter a fourth cycle is fully developed, and the 

 total number of seipta in the calice is thus 40. The primaries 

 are conspicuously longer and broader than the rest, which 

 are subequal. 



The central fossa is long, wide, and shallow, and is bounded 

 by the free margins of the septa. The columella is formed by 

 the fusion of processes from the principal septa in the manner 

 already described. The papilli on its surface are irregular 

 in shape, numerous, and spreading, especially in the lateral 

 boundaries of the fossa. 



The wall is stout, and the costae, which are continuations of 

 the sCipta, are prominent and ornamented with transversely" 

 elongated granules. Those on the flat surfaces of the corallum 

 are broadest at the calicular margin, and gradually taper down- 

 wards, while those on the edges contract medially, but again 

 eXipancl as they approach the base. In some examples, pro- 

 bably aged ones, the costee on the edges are distinctly broader 

 than those on the flat surfaces, but usually the difference is so 

 slight as to be easily overlooked. The two lateral primaries 

 are curved, and follow the contour of the corallum from tlie 

 calicular margin to the pointed base. The remaining costse 

 are straighter, and almost parallel with each other. The 

 several orders are nearly or quite free to their basal termina- 

 tions, with the exception of the more central pair of quater- 

 naries in each end system, which fuse with the enclosed ter- 

 tiary at a half to two-thirds from the margin of the calice. 



Height of corallum, 8.5 mm. ; length of calice, 6 mm. ; 

 breadth of calice, 4 mm. 



Locality, &c. — Fairly abundant in Eocene strata at Wilkin- 

 son's No. 4 Aire coastal section and at Spring Creek, near 

 G-eelong. The type is from the foraier locality. 



Platytpoehus hastatus, '<pp.c. nov. 

 PI. v., figs. 2a, b. 



This species is smaller and more slender than the preceding, 

 and has a prolonged, spear-shaped base. Tlie cost?e also are 

 smooth, and rarely there is a shining, but very faint epitheca 

 partially covering them. In typical examples the cost?e of the 

 edges and flat surfaces differ very little in size, but the former 

 tend to become broader with age, and then the coral approxi- 

 mates in outline to P. vacuus, T. Woods, see post, which is, 

 however, a more compressed form. 



