THE BIOLOGY OF WOOD-BORING TEREDINID MOLLUSCS
375
I n respect of the intestine, shipworms are of two types: (1) those in
which this takes a forward course into the foot where it loops over the
style-sac; and (2) those in which it does not loop over the style-sac.
Bactronophorus, Neoteredo, Dicyathifer, Teredothyra, Teredora, Uperobus, Psiloteredo, Nototeredo norvagica and N . knoxi are in the former
category while Teredo, Lyrodws, Nototeredo edax, Spathoteredo, Nausitora and Bankia are in the latter.
FIG. 17. Bankia indica. (=B. carinata). The coiled typhlosole of the intestine.
A longer and coiled mid-gut is characteristic of less specialized
shipworms. The length of the mid-gut also varies considerably in
different genera. Nototeredo norvagica has a highly coiled mid-gut. In
species of Teredora and Psiloteredo the gut characteristically loops over
the style-sac. In Teredo, Bankia and Nawsitora, She mid-gut makes a
sharp backward turn beyond the dilated portion containing the
coiled typhlosole of the intestine and so is comparatively short.
At the beginning of the mid-gut in certain shipworms (Bankia,