456 
The right valve is invariably but slightly convex, so far as my own observation 
has gone, and the umbo insignificant. The valve is, however, traversed by a much 
larger number of cost® of both orders, but there is no appearance of the ridges on 
the anterior dorsal margin. Both valves have the intercostal spaces concentrically 
traversed by very fine delicate wavy lines (PL 22, figs. 1-3); indeed, this appears to be a 
character common to the whole group (PI. 23, figs. 1-3). The right valve at times 
assumes a transversely elongated outline, giving to it a most unusually inequilateral 
appearance. This seems to be caused by a prolongation or extension of the depressed 
anterior end (PI. 22, fig. 4), and is particularly noticeable in specimens from the Croydon 
Gold Pield. 
The large adductor impression in the right valve is nearly central, and is con- 
nected by a line of muscular points of attachment to a deep and pit-like excavation 
under the inflection of the area. This, in casts, appears as a sharp projecting point. 
On the anterior side of the adductor the muscular attachments become clustered, and 
are placed at some considerable distance from the anterior margin. 
The resemblance of Maceoyella Barlclyi to Pseudomonotis yarforthensis. King, 
has been already dwelt on. With M. umhonalis, Moore, and M. corhiensis of the same 
author, we are at present not thoroughly acquainted, but it would appear that the 
very central position of the umbonos in the former, the increased convexity in the 
latter, and the more numerous and regular radiating cost® in both may be taken as 
points for future separation— that is, supposing these shells to be separate and valid 
species. 
Through the kindness of Mr. G. W. De Vis, I have been able to examine 
the shell named Sfreptorynchtis Davidsoni* by Mr. R. Etheridge, E.R.S., which 
formed a portion of Mr. Daintree’s Collection. I find it to be an undoubted Mac- 
coyella, either M. reflecta, or this species, probably the latter, and is cither from 
Wollumbilla, or the Walsh River, it being rather difficult at times to distinguish the 
matrices apart. 
A rather worn specimen (PI. 23, figs. 1 and 2), is provisionally united with 
M. Barhlyi, as it appears to accord better with that species than with M. reflecta. The 
shell, measuring nearly two and a-half inches square, is larger than the generality of 
individuals of the former. It is from the Walsh River. 
In PI. 22, fig. 3, 1 have given an illustration of the Maryborough variety of 
M. Barhlyi, which is distinguished by the size and rugosity of the primary cost® and the 
development of the posterior spines ; and it is, in addition, a smaller shell. In an 
internal cast from this locality the cost® also appear to terminate along the front 
margin in a series of free spines. Similar features are j^rcsent in the form of our shell 
from Croydon (PL 42, fig. 5). 
Loc. Wollumbilla {^The late JRev. W. B. Clarice) ; Walsh River {lion. A. 0. 
Gregory ) ; Bungeworgorai Creek, near Mount Abundance ; Blythesdale Station, 
between Wollumbilla and Roma; Maranoa River, at Mitchell f {G. Sweet — Colin. 
Sweet, Melbourne). In South Australia at Peak Creek {Messrs. J. S. Chandler 
and J. Canliam J) ; and forty-five miles south-west of Cootanoonna, Lake Eyre 
{M. Y. L. Brown — Colin. Nat. Hist. Mus., London). Occurs also in the Desert 
Sandstone. 
* Quart. Joum. Geol. Soc., 1872, xxviii., p. 333, t. 17, f. 1. 
+ With the valves in apposition, and the best examples I have seen. 
t Teste Tate, Trans, E. Soe. S. Australia for 1879-80 [1880], iii., p. 179; Ibid., 1880-81 [1882], iv., 
