THE MOLLUSCA—HEDLEY. 505 
axe heads.* The natives of the Solomon Islands prefer fossil to 
recent shells for this purpose. { 
What information we have, suggests that the range of this 
species is almost co-extensive with that of the reef-building 
corals. 
Weights and measures of sundry large individuals have lately 
been published by Smith, t his maximum record being five hundred 
and seven pounds weight, and fifty-four inches in length. This is 
almost reached by an unquoted record from the Isle of Pines, New 
Caledonia. Dr. T. Mialaret writes$:—“ In the middle of the 
peninsula which encloses the Bay of Oupion the east, there occurs, 
sunk in the coral, the edges of its valves level with the surface of 
the rock, a gigantic Z’ridacna measuring at least 1 metre 20 in 
length. At the request of Admiral Courbet, we attempted in 
1882 to extract it, but all our efforts were in vain.” 
The genus Z'ridacna appears to suffer from a superfluity of 
specific names. No characters of permanent value separate ils 
squamosa from 7’, gigas. These forms are usually if not invariably 
free.|| On the contrary, the habit of 7. elongata is to bury itself 
in rock, a habit always causing variability in shape. 
Hanley states that it was upon what Lamarck called ‘ 7’. 
squamosa” that Linne himself founded his Chama gigas.{| 
TRIDACNA ELONGATA, Lamarck. 
Reeve, Joc. cit., pl. ii.; Valliant, Ann. Sci. Nat., iv., 1865, pp. 
65 — 172, pls. viii. — xii. 
This species is abundant, perforating dead coral in the Funafuti 
lagoon. So firmly does the foot adhere, that when wrenching the 
shell out of its burrow, I have sometimes torn the animal asunder, 
leaving the foot attached to the rock. The position of the shells 
embedded in dead coral is well displayed in one of W. 8. Kent’s 
photographs.** 
The natives, who distinguish it from the preceding as ‘“ Fasua 
noa,” also use it as food. 
The range of 7’. elongata appears to exceed that of 7’. gigas, 
the furthest southern point reached by it in the Pacific being 
Lord Howe Island. 
* Valliant— Bull. Soc. Geol. Fr., xxv., 1868, pp. 681 - 687. 
+ Willey—Nature, Oct. 1896, p. 523. 
t Smith—Proc. Malace. Soc., iii., 1898, p. 112. 
§ Mialaret—L’ Ile des Pins, son Passé, son Present, son Avenir, 1897, 
p. 63. 
Kent—Great Barrier Reef, 1898, pp. 44-45, pl. xxix. 
« Hanley—Ipsa Linnzi Conchylia, 1855, p. 85. 
** Kent—Loc. cit., foreground of No. 1, pl. iv. 
It 
