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LAMELLIBRANCHIATA. 
Ambonyehia macroptera, spec. nov. PI. ii., fig. 10. 
Shell very small, obliquely triangular, sub-convex, umbones 
terminal ; ornamented by numerous slender radial ridges about 
as wide as the alternating furrows; posterior margin medially 
subangulated. 
Wing nearly as large as the valve, much _ expanded 
posteriorly, with a prominent fold or border on its ventral 
margin, separated however from the hinge-line by a deep 
suture; superior to the marginal fold the surface is broadly 
depressed, the dorsal margin is straight but ascending. The 
surface is marked by sigmoidal growth-folds, and the posterior 
margin is coincidently curvilinear. 
Dimensions.— Oblique axis, 3-5; transverse axis, 2°5; width 
of wing at posterior end, 2°5 ; its oblique axis, 3 millimetres. 
Locality.—Cambriam limestone at  Curramulka (three 
examples). 
PALLIOBRANCHIATA. 
Orthisina compta, spec. nov. PI. ii., figs. 6-6a. 
Transversely subquadrilateral, equilateral; hinge nearly straight, 
not quite so long as the greatest width of the valve. 
Dorsal (?) valve flatly convex with depressed anterior- and 
posterior-ventral areas, which are separated by a submarginal 
roundly elevated medial fold. 
Surface marked by distant, broad undulations ; in the umbonal 
area these have a rhomboid outline, but towards the front are 
medially incurved, coincident with the curvature of the ventral 
margin ; the folds and intervening furrows are distantly and 
coincidently linear-striate, and ornamented radially by depressed 
subangular plications (about 30), which are wider than the inter- 
stitial furrows. Hinge area with a subquadrate, subconvex, 
nearly vertical median projection, flanked on each side by a 
linear-lanceolate, longitudinally plicate-striate area. 
Dimensions. —_Length of hinge-line, 7; greatest antero-posterior 
diameter, 9 ; greatest umbo-ventral diameter, 6. 
Locality.—Cambrian limestone at Curramulka. 
Orthis (?) peculiaris, spec. nov. Plate ii., fig. 5. 
Transversely subquadrilateral, equilateral; hinge-line in the 
longest antero-posterior diameter, straight. 
Ventral (?) valve flatly convex, with an abruptly depressed and 
deeply bilobed ventral margin; the mesial furrow decreases in 
depth as it ascends to near the umbo; the lateral margins are 
obliquely arched, nearly straight, forming an angle of about 70° 
with the hinge- line. 
Surface marked by depressed unequal folds of growth. 
N 
