306 Canadian Record of Science. 
OBOLUS PULCHER, N. sp. 
Fig. 1. Ventral valve. Natural size. 
“2. Same, mag. 23, to show the surface markings. The dotted line near 
the top of the figure indicates the outline of the dorsal valve at that part. 
Fig. 3. Embryonic shell, Dorsal valve, mag. +5. 
** 4. Same, seen from behind. 
«“ 5. Same, seen from the side. 
‘** 6, Embryonic shell, Ventral valve, mag: 4°. 
“7. Same, seen from behind.! 
““ 8. Same, seen from the side. 
General outline nearly orbicular; the valves gently, but 
rather flatly and evenly arched down from the centre all 
around, except that the dorsal is flatter at the back than 
elsewhere, and the ventral valve runs out into a short acu- 
minate umbo. 
Dorsal valve somewhat wider than long; more strongly 
arched towards the front than elsewhere ; somewhat elevat- 
ed at each end of the hinge line. 
Ventral valve about as wide as long, sides and front even- 
ly rounded ; back produced into a short pointed beak, angle 
of incidence of the two sides, 110° to 120°. 
Sculpture of the posterior half of the valves, consisting 
of minute tubercles, sloping forward, and arranged in rows, 
which arch forward across the mesian line from each late- 
1 The angle at each side is an error of the engraver. 
