A MONOGRAPH OE THE TERTIARY POLTZOA OF VICTORIA. 13 



14. O. hastata, Busk. PI. I., figs. 21, 22, 23. 



C. hastata, Busk, B.M.C., Pt. I., 7 ; id. C.P., 10 ; McG., P.Z.V., 24. 



Zocecia ovate ; front with a scutiform area, having on each side 5-9 fenestrse, 

 between which are usually lines or fissures converging to a central line ; thyrostome 

 straight below, with an internal denticle (usually absent) on either side. 



S.P. ; M.C. ; B.R. and W.P. (W.). A common living Australian species. 



The large lateral processes, so characteristic of the recent specimens, are 

 wanting in the fossils, having been broken or worn off, but I think there can be 

 little doubt of the identification. It is a very variable species, recent specimens 

 differing in the form and size of the zocecia, the form of the scutiform area, the 

 number and appearance of the fenestrse, and the shape and size of the lateral 

 processes. Normally the fenestrse are the openings of short horizontal tubes, but 

 these are frequently indistinguishable, and the pores seem to open directly inwards. 

 The lateral processes usually have the supra-avicularian portion pointed upwards, 

 while in a common very massive form, which I was at one time inclined to describe 

 as a new species, the lateral processes are thick, blunt or rounded above and 

 considerably turned forwards. In the fossils the opening of the fenestrse into tubes 

 is usually very apparent. The zocecia are generally narrower than in the recent. 

 They are also frequently produced above the thyrostome, and there is then a distinct 

 narrow longitudinal ridge, which is absent in the recent specimens, owing to the 

 thyrostome being situated almost at the summit of the zocecium. 



15. C. retroversa, n.sp. PL I., fig. 24. 



Zocecia broadly ovoid or elliptical ; a row of fenestrse, about six on each side, 

 round the margin, with grooves radiating from the central line ; thyrostome large, 

 lofty, straight below; lateral processes very broad, extending the whole length of the 

 zocecia and turned backwards ; a marginal avicularium at each upper angle opening 

 directly outwards. 



M.C. 



Allied in structure to C. cribraria, but distinguished at once by the broad, entire, 

 retro verted lateral processes. 



16. C. marginata, Waters. PL I., figs. 25, 26, 27. 



C. marginata, Waters, Q.J.G.S., August, 1881, p. 317. 



Zocecia elongated, nearly cylindrical ; thyrostome large, straight below ; 8 or 9 

 fenestrse enclosed by a narrow, prominent, raised ridge ; zocecia produced above the 



