46 THE ZOOLOGIST. 
peduncle and the valves of the capitulum having excellent and 
often renewed rasping surfaces; and, lastly, by the end of the 
peduncle (that is, homologically, the front of the head) thus 
roughened extending beyond the surface of attachment, and 
possessing the power of slight movement.’ Many crustaceans 
perforate sand, clay, mud or sandy mud, while two at least 
(Chelura terebrans and Limnoria lignorum) are well-known de- 
stroyers of wood. 
The first of these (Chelura terebrans) is a form less familiar to 
Scottish zoologists—especially those on the eastern shores—than 
to our southern colleagues. It is abundant, however, on the 
southern and western coasts and in Ireland, its range likewise 
extending to many parts of Europe and the United States. A 
similar form (Chelura pontica) is also described by Czerniavsky 
as occurring along with Teredo in the Black Sea, while elsewhere 
it is generally associated with the other form, Limnoria. In 
xylophagous powers it is even more destructive than the latter, 
since its excavations in timber are considerably larger and more 
oblique, the wood being ploughed up rather than bored into, so 
that the surface thus undermined is rapidly washed away by the 
action of the sea. In one of the many beautiful memoirs 
written by the late Prof. Allman, formerly the distinguished 
occupant of the Chair of Natural History in the University of 
Kidinburgh, a description is given of these crustaceans in the 
timber-piles of the jetty of the Harbour of Kingstown, near 
Dublin. It has been calculated that Chelura will destroy a piece 
of Memel timber thirteen inches square in less than ten years, 
working from the level of the mud almost to the height of neap- 
tides. It is believed that the mandibles of the animal enable it 
to perforate the moist timber, which it swallows. The mouth- 
organs consist of an upper and a lower lip, a pair of mandibles, 
and two pairs of maxille. Between the spines and the base of 
the mandibles is an oval elevated surface marked with transverse 
ridges, which are again crossed at right angles by delicate striae. 
Prof. Allman considered that this eminence constitutes a very 
efficient grinding surface. The last pair of appendages at the 
tail of the animal are remarkable in size and length, and pro- 
bably aid in effecting various movements within its chamber, as 
well as in leaping (after the manner of a Springtail) when placed 
