K. L. Prendergast. 
3() 
A. medlic\ottianus\ therefore, since those things which are equal to the same 
thing are equal to one another: — 
A. tibeticus == A. giga-^, 
therefore Wyatkina — Strophalosiina. 
If the ])remises are true Strophalosiina is a synonym of Wyatkina. The 
author has not been able to see the original description and figures of 
A. gigas, so cannot discuss its affinities with A. tiheticus. The diagnostic 
feature of .^1. tiheticus is the ornamentation, and later writers on A. gigas 
do not describe that shell as radially plicate. 
Until further information is available, Stroplialosuna and Wyatkina are 
accepted as subgenera of Aulosteges. 
Aulosteges spinosus Hosking. 
PI. iv, figs. 7-10. 
1981 . — Aulosteges spi}ws-us Hosking, p. 17, pi. iii., figs. 7a-d, 
1938 . — Aulosteges spi7iosus Hosking, p. 37. 
Material. — Aus. Mus. F 38444, 37710, Wandagee Station, Minilya River,. 
North-West Division. Wandagee Stage. 
Diagnosis. — Shell small to medium in size, subquadrangular, wider than 
long. Surface of both valves with small perforated tubercles bearing small 
spines. 
Pedicle valve convex, not swollen, faint median sinus. Umbo high, not 
overturned, Area broad, slightly concave and recurved to cardinal margin^ 
j^seudo-deltidium narrow, highly arched. 
Brachial valve flat, triangular extension of cardinal margin large. 
Internal features unknown. 
Description. — For complete description of this species reference should 
be made to Hosking (1981, p. 17 et seq.). 
Two rather dissimilar sj)ecies from the North-West Division are here 
referred to this species. 
Dimensions. 
Length 
Type : 
18-8 
38444. 
45*1 -f 
37710. 
20 
Breadth .... 
19-7 + 
43-0 -f 
22 
Length of hinge-line 
14-5 
21-3 + 
15 
Thickness 
— 
7-4 

F 38444 is a com])Iete specimen with both valves. The umbo is distorted 
by a cicatrix of attachment and twisted slightly to the left. The area is high 
and very worn so that no growth lines or transverse striations are prescr\'ed. 
It has the same recurving to the cardinal margin as noted by Hosking in 
the description of the holotype. The pseudo-deltidium is narrow and parallel- 
sided; it has twisted, with the twisting of the umbo, to the left. An indenta- 
tion of the valve, as the beginnings of a median sinus, occurs near the 
anterior margin. The ornamentation of the pedicle valve is of fine forward- 
projecting spine bases. 
