THE HIOLO(:Y O F WOOD-BOllIN(: TEREDINID MOLLUSCS
365
end of the tube may be partially or completely divided by a calcareous
longitudinal partition, the inhalant and exhalant siphons each extending through a half of the partitioned tube (Turner, 1966).
5 . The siphons
The formation of siphons in the bivalves has been described by
Yonge (1948) and those of shipworms are referable to the type B/C
(Yonge, 1957). They have been described by Sigerfoos ( 1908) in Bankia
gouldi, by Roch (1940) in Teredo utriculus, by Nair (1957a) in Bankia
indica, by Bade et al. ( 1961) in Bankia minima, by Turner (1966) in
Nausitora fusticula, Teredora malleolus and Bankia rochi and by
Saraswathy and Nair ( 197 I ) in Nausitora hedleyi. Their appearance,
whether united (except at the tip), partially separate or separate, in
34 species has been presented by Turner ( 1 966) who further suggested
that siphonal characters such as length, extent to which they are
separated, the number and size of the papillae and the colour and colour
pattern, may prove useful in systematic work and might be of great
assistance in the identification of species by the aid of the displayed
siphons without disturbing the animal. That the characters of the
siphons do exhibit distinguishable variations (Fig. 12) which may be of
taxonomic value is evident from the observations of Roch (1940) on
Mediterranean species and of Clapp ( 195 1 ) on Teredo sigerfoosi. Morton
( 1 970) finds specific differences between the siphons of T . navnlis and
Lyrodu.3 pedicellatus. For detailed anatomical studies the work of Nair
(1 957a) and Saraswathy and Nair ( I97 I ) should be consulted.
6. The boring m~chonisir~
The ability to bore into hard substrata is a habit which has evolved
independently in no less than seven super families of the Bivalvia. In
the Adesmacea this ability appears t o have been derived from the
primitive infaunal burrowing habit by adaptation to deep burrowing in
stiffer and stiffer substrates until true boring was developed. In all
other groups, with the exception of Platyodon, the sole boring genus of
the superfamily Myacea, true boring probably developed as a further
specialization of an epifaunal, byssally-attached existence on rock and
especially of the habit of nestling in crevices (Yonge, 1963). The
structural modifications of the basic bivalve form associated with the
boring habit liiive beeti extensively studied (Miller, I924 ; Yurchon,
1955). All the niembers of' the Adestnucea show considerable modificatioti t o boring, but those of t h e Pholadidae which bore into rock and
other solid substrates including peat, sandstone, limestone, shale and
mudstone are less specialized than members of the X ylophaginidne
365
end of the tube may be partially or completely divided by a calcareous
longitudinal partition, the inhalant and exhalant siphons each extending through a half of the partitioned tube (Turner, 1966).
5 . The siphons
The formation of siphons in the bivalves has been described by
Yonge (1948) and those of shipworms are referable to the type B/C
(Yonge, 1957). They have been described by Sigerfoos ( 1908) in Bankia
gouldi, by Roch (1940) in Teredo utriculus, by Nair (1957a) in Bankia
indica, by Bade et al. ( 1961) in Bankia minima, by Turner (1966) in
Nausitora fusticula, Teredora malleolus and Bankia rochi and by
Saraswathy and Nair ( 197 I ) in Nausitora hedleyi. Their appearance,
whether united (except at the tip), partially separate or separate, in
34 species has been presented by Turner ( 1 966) who further suggested
that siphonal characters such as length, extent to which they are
separated, the number and size of the papillae and the colour and colour
pattern, may prove useful in systematic work and might be of great
assistance in the identification of species by the aid of the displayed
siphons without disturbing the animal. That the characters of the
siphons do exhibit distinguishable variations (Fig. 12) which may be of
taxonomic value is evident from the observations of Roch (1940) on
Mediterranean species and of Clapp ( 195 1 ) on Teredo sigerfoosi. Morton
( 1 970) finds specific differences between the siphons of T . navnlis and
Lyrodu.3 pedicellatus. For detailed anatomical studies the work of Nair
(1 957a) and Saraswathy and Nair ( I97 I ) should be consulted.
6. The boring m~chonisir~
The ability to bore into hard substrata is a habit which has evolved
independently in no less than seven super families of the Bivalvia. In
the Adesmacea this ability appears t o have been derived from the
primitive infaunal burrowing habit by adaptation to deep burrowing in
stiffer and stiffer substrates until true boring was developed. In all
other groups, with the exception of Platyodon, the sole boring genus of
the superfamily Myacea, true boring probably developed as a further
specialization of an epifaunal, byssally-attached existence on rock and
especially of the habit of nestling in crevices (Yonge, 1963). The
structural modifications of the basic bivalve form associated with the
boring habit liiive beeti extensively studied (Miller, I924 ; Yurchon,
1955). All the niembers of' the Adestnucea show considerable modificatioti t o boring, but those of t h e Pholadidae which bore into rock and
other solid substrates including peat, sandstone, limestone, shale and
mudstone are less specialized than members of the X ylophaginidne