FOSSILS OF NEW SOUTH WALES. 697 
less than a right angle with those of the lateral surface. The shell appears to have been 
quite thin ; portions remaining are much less than half a line in thickness. The lateral 
surface must have been a little flattened, and the lower margin, judging from the direction 
of the rugee, was nearly or quite straight at middle. 
40. Mmonzta myrFormis (Dana).—Rather thin; inequilateral ; oblong elliptical, with 
the beak little prominent, and the lower margin nearly straight; not narrowing behind, 
nor carinate, posterior and anterior margins equally arcuate. Exterior surface smooth, 
with only faint strice of growth. Sides compressed. Palleal impression and _ posterior 
muscular indistinct. Larger anterior muscular impression excavate above. Cast of 
extremity of beak a slender point-—Length 2 inches ; height 61, L.; thickness about 5°55 
L. or 5%; H.; apical angle about 148°.—Plate 6, fig. 4 a, interior cast of a valve ; b, 
front view of same; c, view of cast of hinge. 
Wollongong Point, District of Illawarra. 
This species is distinguished by being thin, not narrowing behind nor carinate, and 
surface smooth. This last character, and its less arcuate lower margin, distinguish it 
from the following. 
Pyramus myiformis, Exped. Foss., Amer. Jour. Sci., 11. Ser., iv. 157. 
41, Monza Evirprica (Yana).—Rather thin ; inequilateral, oblong elliptical, narrow- 
ing a little behind, not carinate, lower margin, and also the anterior and posterior, arcuate. 
Right valve rather highest. Surface evenly convex, concentrically marked with smooth 
unequal ridges and strie of growth. Palleal impression faint, anteriorly plicatulate. 
Posterior muscular impression faint, anterior less so, Lateral surface of cast a little 
flattened, cast of beak acute.—Length 17 to 3 inches; height 54% L.; thickness ;41; L., or 
$5 H.; apical angle 137°.—Plate 6, fig. 5 a, b, c, different views, natural size ; fig. 6, cast 
of a larger specimen ; 6 a, cast of hinge of left valve. 
Harper’s Hill, valley of the Hunter 7—Wollongong, Illawarra. 
The strize on the smaller muscular impression are distinct; they cover the outer side, 
and curve around it in front. 
Pyramus ellipticus, Exped. Foss., Amer. Jour. Sci., ii. Ser., iv. 157. 
42, Mmonta o1cas (IM’Coy) Dana.—Thick, ventticose, very inequilateral, oblong, 
height two-thirds the length ; beak large and incurved ; posteriorly narrowing, somewhat 
dilated, and behind obliquely truncate ; flank flattened, but without a very distinct carina, 
Sides compressed, or slightly excavate, and inferior margin straight or a little excavate 
near middle ; lateral surface marked with concentric strie. Valves very thin.—Length 
5$—7 inches ; height 73, L. 
District of Illawarra. 
This species has the large size and thin shell of the following species, but is not regu- 
larly convex, the sides being somewhat compressed, and it is longer for its height. 
Pachydomus gigas, M’Coy, loc. cit., p. 301, pl. 16, fig. 3. 
43. Maonta cranpis (Dana).—Thick, ventricose, inequilateral, sides regularly con- 
vex, not at all carinate, narrowing somewhat posteriorly, and posterior margin arcuate ; 
175 
