Miscellanea. 325 



Pachydomus gigas (M'Coy). PL XVI. fig. 3. 

 Sp. Char. Transversely oval, length two-thirds of the width, very 

 gibbose, inflated ; beaks very large, incurved, placed in about the 

 anterior third of the shell ; posterior side obliquely truncated, 

 the angles rounded; posterior slopes compressed, flattened; pos- 

 terior ndge obtusely rounded, almost disappearing before reaching 

 the posterior inferior angle ; anterior side small, narrowed, with 

 a slightly marked sinus between it and the convex ventral margin ; 

 surface marked with small conceniric cord-like sulci and ridges. 

 This IS distinguished from the P.glohosus (with which Mr. Morris 

 seems to include it) by its greater width in proportion to the length, 

 by the flattened, compressed sides of the posterior slopes and the 

 more oblique truncation of the posterior end, and the smallness and 

 narrowed appearance of the anterior side, arising from a slight, but 

 always perceptible, sinus betw^een it and tlie convexity of the ventral 

 margin. The shell is very thin in this species, which makes a near 

 approach to Leptodomus (M'Coy) in all its characters. Length 4^ 

 inches, width 6 inches 3 lines (often nmch larger). 



Common in the fine sandstone of Wollongong, N. S. Wales. 



Pacliydomus sacculus (M'Coy). PI. XIV. fig. 5. 



Sp. Char. Subquadrate or satchel-shaped, length nearly equalling 

 the width, thickness two-tliirds the length ; gibbose towards the 

 beak, compressed towards the ventral margin ; beaks large, nearly 

 central, strongly incurved towards the anterior side; posterior 

 side forming a short, compressed, rectangular wing ; anterior side 

 very obliquely truncated ; anterior and posterior slopes abruptly 

 rounded, and the angles formed by their junction with the ventral 

 margin equal, broadly rounded and nearly equidistant from the 

 beak ; abdominal margin broadly concave, giving the middle of 

 the valves a flattened, slightly hollowed appearance ; shell very 

 thick, foliaceous ; surface with a few obtuse concentric elevations 

 and numerous irregular concentric lines of growth. 

 Length 4^ inches, width 4 inches 9 lines. I am uncertain whether 



the specimen figured is from Black Head or Wollongong, N. S. Wales. 



Pacliydomus ovulis (M'Coy). PL XIV. fig. 4. 



Sp. Char. Transversely oval, length five-sixths of the width, com- 

 pressed, thickness rather more than two-thirds of the length; 

 beaks tumid, nearest the anterior end; anterior and posterior ends 

 oval, rounded, the latter obscurely angulated at end of hinge- 

 line; ventral margin regularly convex; surface marked with 

 thick, unequal, cord like concentric strise, lunette deep ovate ; 

 ligament external, large. 



The anterior and posterior adductor impressions are large and 

 oval ; the impression of the retractor of the foot very small, lu- 

 nate, just over the anterior adductor ; pallial impression with a 

 small rounded sinus before joining the posterior adductor. Distin- 

 guished from the P. (oevis. (Sow.) by the coarse concentric lineation 

 of the surface. Length 1 inch 8 lines, width 2 inches. 



Very common in the sandstone of Wollongong, N. S. Wales. 



Pachydomus ? pusillus (M'Coy). PL XVI. figs. 1 & 2. 

 Sp. Char. Small, ovato-orbicular, width slightly exceeding the 

 length, globose, thickness four-fifths the length; beaks very 



