CHELURA TEREBANS. 
505 
dilated peduncle which is as broad as long, and fur- 
nished upon the inner margin with two hooked spines 
and a few plumose cilia. The antepenultimate pair of 
caudal appendages have the peduncle long and narrow ; 
the branches are short : the penultimate pair have the 
peduncle developed into a large thin plate, produced 
upon its inner margin to a breadth quite equal to its 
length ; the branches are short, equal in length, the 
inner one being not quite so broad as the outer: the 
ultimate pair have the peduncle very short, but as if 
to compensate, the branch is greatly developed, being 
about the length of the inferior antennae, and is very 
broad, especially near the base, and flattened. The 
middle tail-piece is of the form of a broad lance-head, 
attached to the animal by a short foot-stalk. 
This species is one of our most injurious xylophagous 
Crustaceans. It is commonly found associated with Lim- 
noria lignorum , but, fortunately for piles and other marine 
woodwork, it is not so prolific as that species. Its 
excavations, are, however, much larger and more rapidly 
executed. It is in fact so destructive that it will destroy 
a piece of Memel timber thirteen inches square in less 
than ten years. It works into the timber from the level 
of the mud to nearly the usual height of neap tides, 
avoiding, however, the knots of the wood. In this 
manner the wood is riddled in every direction, and is 
easily acted upon by the force of the water. 
We have no doubt but that it excavates the saturated 
wood for the purpose of food ; but we are unaware as 
to the manner in which the canals in which it resides 
are made. Our first impression is, that the mouth is the 
perforating organ, and the beautiful grooved surface of 
the under plate on the inner edge of the mandibles — 
carefully figured by Professor Allman in his elaborate 
