250 
Orthis (tW Orthisina), ^;j. 
(Plate XXV., fig. 9.) 
Ohs. — I regard this as distinct from 0. tatet. The valve 
is a single specimen, apparently the pedicle, and is sub- 
quadrilateral, convex, the greatest convexity at about mid- 
way in the length of the valve, the sinus gradually deepening 
and widening towards the front, and bounded laterally by 
ill-defined folds, one on either siae, the surface sloping away 
on either side rapidly to the lateral margins, and at a very 
much less angle within the sulcus : there are indications of 
costae on the divaricating folds and in the sulcus. 
The hinge features are hidden in matrix, nor is the umbo 
distinctly visible ; it may, therefore, be either an Orthis or 
an Orthisina. 
It is quite distinct from either Orthis ( I ) jpeculiaris, 
Tate,^ or Urthisina co7npacta, Tate,t but in general appear- 
ance it resembles Orthis f ?) spiriferoides, McCoy,J a Caradoc- 
Bala species. 
In the Archaeocyathinse white limestone at Wirrialpa. 
Orthis {rel Orthisina), sp. 
(Plate XXV. fig. 10.) 
Ohs. — In the same white marble occurs another Brachio- 
pod, which may belong to either of the above genera, the 
same disabilities rendering it impossible to arrive at a satis- 
factory conclusion, as in the preceding instance. 
This valve, again a single example, I take to be the 
brachial. It is rotundato-quadrate, the cardinal margin as 
long as the width of the valve, the surface convex, except on 
the dorso-lateral alations, where it appears to be flattened. 
There is a central, acute, or pinched-up fold, produced for- 
ward, and expanding as it advances. There are indications 
of the existence of strong, distant, sub-radiating costae. 
Whether or no this is the brachial valve of the species 
represented by the preceding form, it is, at present, impos- 
sible to say ; the two occur in the same bed, however. There 
is a strange resemblance in the pinched-up fold to the same 
portion on the brachial valve of a Caradoc species, Orthis ves- 
pertilio, Sby.>$ 
In the Archasocyathinae white limestone at Wirrialpa. 
* Tate— Tr.R.S.S.A., 1892, xv., part 2, p. 185, t. ii., fig. 5. 
+ Tate— loc. cit., p. 185, t. ii., figs. 6, 6a. 
+ Davidson — Mon. Brit. Sil. 15rach., part vii.. No. 4, 1871, 
p. 275, t. xxxvii., fig. 3a. 
§ Davidson — Mon. Brit. Sil. iirach., No. 3, t, xxx., figs. 
11, 12a. 
