63 



On a Fossil Marine Diatomaceous Deposit from Oamaru, 



Otago, New Zealand. 



By E. Grove and G. Sturt, P.F.R.M.S. 



Part III. 

 Plates V. and VI. 



{Taken as read March 25th, 1S87.) 



Trinacria ventricosa, n. sp., Gr. and St. — In this species we 

 have two dissimilar frustules alternating with each other. The 

 primary valve, as it may be called, has slightly concave sides 

 with a clear margin. The centre is moderately inflated with a 

 small circular umbilicus, usually surrounded by a ring of pear- 

 shaped cellules, the remainder of the surface being covered 

 with large, irregularly radiating granules. Processes straight, 

 elongated, like those of Trin. regina, Heib., to which this 

 valve bears a general resemblance. 



The secondary valve has a large inflated centre, leaving at 

 each corner a flat triangular space, on which is the indication 

 only of a nodule. Surface dotted with papillae, presenting at 

 the margin a rugose appearance. 



Length of sides of valves usually about , 005' / . From several 

 specimens observed in contact, it appears that these two forms 

 belong to the same filament, and that the pseudo-noclules of the 

 secondary valves meet and are continuous with the processes of 

 the primary valves, also that the inflations meet one another, 

 touching at their apices. Frequent. 



PI. V., Fig. 1, primary valve ; Fig. 2, secondary ditto ; Fig. 3, 

 frustular view. 



T. ligulata (Grev.), Gr. and St. (Triceratium ligulatum, Grev., 

 " T. M. S.," Vol. xii. p. 91, PI. 13, Fig. 9).— Corresponds with 

 Greville's figure, which is clearly a Trinacria. It is probably 

 only a small variety of T. excavata, Heib. Length of side, *003 // . 

 Frequent. 



Journ. Q. M. C, Series II., No. 18. 6 



