MARINE WORMS. 345 



feet above low water, and it has been found to work down 

 to some 2 feet 6 inches below the ground. 1 



It has been stated that the Teredo navalis will not attack 

 timber with the bark on ; this does not appear to be universally 

 correct, although it is a protection to a certain extent. At 

 San Francisco, it was found that many worms did attack and 

 penetrate the bark, but that the greater number died before 

 doing so; the bark once penetrated presents no obstacle to the 

 ravages of the worm. 



At Port Elizabeth, in some jetties erected by Sir J. Coode, it 

 was noticed that the Teredo navalis was more destructive in 

 the horizontal timbers at low water than in the vertical 

 timbers. 2 



The Limnoria Terebrans very much resembles a small wood- 

 louse in general appearance ; it is about \ inch long, of an 

 ash colour, with black eyes. It appears to be furnished with 

 a small mouth and strong teeth, with which it works its way 

 into the softer parts of the timber, following, as a rule, 

 the grain, avoiding the knots and harder parts. It appears 

 to extend its ravages to a higher point above low water than the 

 Teredo navalis. 



The Chelura Terebrans differs from the Limnoria in appear- 

 ance, being more like a minute sand-shrimp, rarely exceeding 

 or | inch in length, and is perhaps the most destructive 

 of all the marine pests. In situations favourable for the 

 exercise of its habits, it soon produces great effects on the 

 wood to which it attaches itself. The borings are so close 

 together that the wood is so disintegrated as to permit of a 

 very moderate movement of the water washing away the 

 surface. The riddled wood is also torn away by small crabs, 

 which prey upon the worm. In the clear water in Malta 

 Harbour, these small crabs could be seen constantly at work, 

 comparatively large holes having been observed in some 

 instances, dug out by these Crustacea. The ends and joints, 

 or where one piece comes in contact with another, appear 

 to be the favourite points of attack ; but under any conditions, 

 an entrance onee effected, the destruction of the timber is rapid 

 and complete. 



In the West Indies, the Lepesma is very destructive, and 



1 Transactions of the Society of Engineers, 1874, p. 112. 

 1 Transactions of the South African Philosophical Society. 



