78 
SHELL GALLERY. 
Fig. 4. 
hinge, the dead valves of dried shells easily fall apart. The peduncle, 
which is sometimes over six inches in length, passes between the 
pointed posterior borders of the valves. Dr. 
Francois gives a very interesting account of 
the habits of Lingida anatina which he found 
living in the sand at Noumea, New Hebrides. 
The sole evidence of the animal's existence 
is the presence, on the surface of the sand 
or mud, of a small, three-lobed slit (Fig. 4, 
upper figure). The tube (Fig. 4) in which 
the Lingula lives is about four inches deep, 
flat in the upper half, rounded below. The 
walls of the upper flat portion simply con- 
sist of the sand with a surface coating of 
mucous secretion ; but in the lower end the 
sand grains are agglutinated so as to form a 
distinct tube. 
The edges of the mantle-folds are pro- 
vided with setae (bristles), which form three 
funnels protruding through the three lobes 
of the slit-like mouth of the sand-tube ; 
currents enter by the lateral funnels and 
leave by the central. 
On the least alarm the animal is rapidly 
withdrawn as far as the centre of the tube 
(see the dotted line of the shell in the figure), 
the surface slit and upper part of the tube 
being obliterated. Each of the arms forms 
a spiral with several coils (Fig. 5). The 
Lingididce, are of exceptional interest, in that 
they furnish a very remarkable example of 
" persistence of type." 
Shells of Lingula occur in the earliest 
Palaeozoic strata, and so closely resemble 
those of the present day, that often no 
difference can be observed either in the shape 
of the valves or in the muscular impressions 
on their inner surface (Fig. 6). 
Lingula occurs in the Indo-Pacific, Aus- 
tralia, China, Japan, and the Pacific Islands. 
Glottidia, a smaller form, with two small 
Lingula anatina in tubes 
in the sand ; upper figure 
shows trilobed opening on 
surface of sand. Dotted 
line in lower figure indi- 
cates position in retrac- 
tion. (After Francois.) 
