231 
the fossil one covering the proper shells, and attaching 
them to the outside of the tube. I hope persons resident 
near the sea will make search to ascertain whether they 
exist, and whether the posterior side is guarded only by 
a membrane. Hitherto naturalists appear to be as much 
in the dark respecting these animals as the animals them- 
selves are in their obscure retreats ; and it is only the fortu- 
nate circumstance of a specimen of petrified wood, in which 
many of them bad been trapped, decaying away from them 
and leaving their outer surfaces perfect, that has permitted 
me to see so much of -their nature. 
TEREDO antenautae. 
TAB. CIL 
Spec. Char. Valves transversely striated ; strise on 
the anterior side numerous, smooth ; dorsal and 
posterior accessory valves shelly. 
Syn. Fistulana per sonata, Delamarck , Foss, des 
env. de Paris , 160. Park • Org. Rem. S p. 200. 
t. 14./. 8. 10. 
The striae follow the zigzag edge of the shell, those over 
the posterior side are very fine and regular, and under a 
lens appear minutely toothed ; on the other side they are 
stronger but less regular and smooth. The dorsal accessory 
valve, called by Delamarck and Parkinson, the rotula , is 
thick, four-lobed, with rounded edges, the two posterior 
lobes are the smallest. The valve that closes the posterior 
sinus is marked with lines of growth parallel to the edges 
of the shell and is very thin; the tube near the valves 
retains, in the large specimens, a wrinkled form, and some 
of the smaller ones are inflated in parts, showing their 
original membranous texture. See figs. 4 and 5. At a dis- 
