234 
tube commences from a very small point outwards at tier 
bottom or sides of the wood ; the embryos were deposited 
in abundance externally very near each other,, they all 
started to pursue their way into the wood in courses more 
or less parallel;, and when any one got before another, 
it seemed to have roamed across the grain, its com- 
petitor being interrupted and apparently stinted by that 
manoeuvre. They sometimes curve and even double and 
have partitions (see fig. 8), but are more frequently without 
any partitions. I have not detected the spatulate valves. 
The connection of the valves with the tube is curious ; the 
dorsal valve is more independent and is rather rare, as it is 
easily detached, and then the beaks of the hinge seem 
perfect, so that it might not be expected by those who had 
not by chance seen it. Fig. 3 is taken from a specimen of 
an uncommon size, the dorsal valve is broken in a way to 
make it irregularly five-lobed, which is too strongly ex- 
pressed in the figure. I have tubes that appear to correspond 
with it from Highgate, they may, perhaps, have been two 
feet long. I have also some parts of tubes from Southend, in 
Essex, and Sheppey, in Kent, full as large in diameter. 
Figs. 5 and 6 show tubes as they appear in the more solid 
masses of Marie when broken. Fig. 6 presents a series of 
undulations not unfrequent and often more extensive. Fig. 7 
exhibits the septum or the lodgments of the two spatulate 
valves at the aperture of the tube, a part very rarely found 
fossil. Fig. 8 has a transverse septum in the wide part 
of the tube. See Park. Org. Rem, Vol. III. p. 205. 
The whole extent of the London Clay stratum and the 
other Clay strata above the Chalk, furnish masses of rotten 
wood perforated by Teredines and impregnated with argil- 
laceous Marie, and Pyrites. The tubes of the Teredines 
are mostly lined with brown and resin-like Carbonate of 
Iron in spicula, &c. 
