28 AUSTRALASIAN ANTARCTIC EXPEDITION. 
PHOLADOMYA ADELAIDIS sp. nov. 
(Plate III., figs. 31, 32.) 
In other features than size and sculpture this resembles P. mawsoni. Shell ovate- 
oblong, little inflated, slightly gaping posteriorly. Surface with about 38 lines of radials, 
the intervals thinly granose. Length, 10; height, 8; depth of conjoined valves, 5mm. 
A single specimen with both valves intact was dredged, December 28th, 1913, in 
288 fathoms, off the Eastern Barrier of Adelie Land, in South Lat. 66° 52’ and Hast 
Long. 145° 30’. The anterior part of left valve, twice the size of type, January 28th, 
1914, from 240 fathoms, in ooze, off the Shackleton Ice-shelf, in South Lat. 65° 20’ and 
Hast Long. 95° 27’. 
PHOLADOMYA ANTARCTICA sp. nov. 
(Plate III., fig. 28.) 
Shell small, ovate, thin, inflated, opaque posterior side twice as long as the anterior. 
Surface uniformly covered with dense, small, sharp grains arranged radially. Lunule 
not defined. Interior nacreous, no pallial sinus. Chondrophore projecting as a small 
spoon process beneath the beak. Length, 12; height, 8-5; breadth of single valve, 
4mm. 
A single right valve, January 28th, 1914, from 240 fathoms, ooze, off the Shackleton 
Ice-shelf, in South Lat. 65° 20’ and Hast Long. 95° 27’. 
PHOLADOMYA MAWSONI sp. nov. 
(Plate IIT., figs. 29, 30.) 
Shell rhomboid-oval, small, very thin, glassy, translucent, beaks at the anterior 
third, valve medially inflated, anterior end short and pouting, posterior end compressed, 
square-ended above, below rounded to the deeply-curved ventral margin, dorsal margin 
rather straight, slightly gaping at the posterior end. Left valve over-reaching the right 
ventrally so that the margin of the right is often tucked in under the left. Beaks low, 
inflated, incurved anteriorly, not eroded Lunular area small, smooth, concave. 
Colour uniform pearl grey. Surface with a silken sheen, devoid of granules, sculptured 
by irregular, delicate, concentric growth striz and traversed by from 25 to 30 narrow 
radiating lines of erect epidermal bristles. These extend across the whole valve except 
the lunule and increase by intercalation. Muscular impressions not visible owing to 
the thinness of the shell. An internal resilium: lies upon an ossicle and is immediately 
beneath the beaks. Length, 13; height, 9; depth of conjoined valves, 6mm. 
This, one of the most interesting shells of the collection, is dedicated to the 
distinguished leader of the Expedition, Sir Douglas Mawson. 
