230 
It somewhat resembles 7'. myodoroides, EB. A. Smith, but 
is smaller, though its proportions are the same. It differs in 
having a concave instead of a straight post-dorsal line, in 
not being excavate in front of the umbo, and in having a 
deeper pallial sinus. 
It differs from 7. modesta, Angas, in being longer pos- 
teriorly, and so more equilateral, and in a vertical trunca- 
tion instead of one sloping upwards and backwards. 
Habitat.—Dredged alive at 9, 20, 22, and 24 fathoms, at 
Port Lincoln, at Yankalilla Bay, and in Backstairs Ses 
Pholadomya arenosa, Hedley. 
Thraviopsis arenosa, Hedley, Proc. Linn. Soc. N.S. Wales, 
1904, vol. xxix., part i., p. 197, pl. ix., figs. 26-27. Type lo- 
cality, 100 fathoms, east of Wollongong, N.S. Wales, one valve. 
Pholadomya arenosa, Hedley, op. cit., 1906, vol. xxxi., p. 
464, Masthead Island, Queensland. 
Mr. Hedley has kindly identified my specimens by com- 
parison with his type. Its dimensions were only 4°55 mm. 
by 2°9 mm; a valve taken in 20 fathoms in Backstairs Pas- 
sage measures 12 mm. by 7 mm. ‘The typical shape and orna- 
ment are retained when adult. 
Dredged alive in 5 fathoms, St. Vincent Gulf; dead in 
Spencer Gulf, Backstairs Passage, and in 62 fathoms north- 
west of Cape Borda. 
p= 
EXPLANATION OF PLATES. 
Pratt XXVIII. 
Kig. 1. Limopsis vixornata, Verco. 
.. 2. Limopsis eucosmos, Verco. 
» 3 Nucula beachportensis, Verco,. 
4. da, 4b. Nuculina (Cyrilla) concentrica, Verco. 
5. Limopsis tenisoni, Ten. Woods, var. peivlevis, Vereo. 
Ga, 6b, Ge. 6d. Sepia braqggi, Verco. 
7. Lissarca rhomboidalis, Vereo, 
Prare XXVIII. 
Big. 1, 2, 3. Trigonia margaritacea, Lamarek, var, bednalli, 
Verco. 
Glycimeris pectinoides, Deshayes; senile state. 
6, 7, 8, 9. Philobrya cuboides, Verco, showing ex 
terior, interior, dorsal view, and umbonal scale. 
» 12, 18, 14. Thracia concentrica, Verco, showing minute 
sculpture, side view, and dorsal view. 
», 15. Hair from Modiola australis, Lamarck. 
16. Hair from Modiola penetecta, Verco. 
17, 18. Modiola penetecta, Verco. 
19, 20. 21. Thracia lincolnensis, Verco, side view, dorsal 
view, and imaginary umbo-ventral section. 
