202 RECORDS OF THE AUSTRALIAN MUSEUM. 



The Teredo tubes penetrate the wood both parallel and at 

 right angles to the direction of growth of the trees, and in either 

 case are more or less parallel and contiguous to one another, or 

 twisted and interlaced in a very confused manner, contorted and 

 even returned on themselves, or crumpled in the form of the 

 letter S. A similar variability in the direction of the tubes 

 is described by Mr. J. Griffith in the great Sumatran Kuplnis,'' 

 during life. In one instance, at least, where half the trunk 

 is preserved transversely, the tubes extend to the very centre. 

 According to the direction of penetration, the tubes are seen 

 in transverse section, longitudinal section, or on the outsides 

 of trunks in the round. The anterior closed ends of the tubes 

 or caps are convex or round, and the diminution in diameter 

 towards the posterior is very slow. The average diameter of the 

 largest tubes at the anterior end is one inch, but a few have 

 been measured as much as one and a quarter inches, and in 

 a single instance the cross section was one and a half inches. 

 These diameters dwindle at the posterior ends to two-eighths and 

 five-sixteenths of an inch. The total length is unknown, but the 

 longest portion measured was six inches. None of the tubes, so 

 far as can be ascertained, are perfect, neither was I fortunate 

 enough to discover in any of the natural sections the valves at 

 the anterior ends, or the forking and septal lamella? towards the 

 posterior terminations. 



The walls are very variable in thickness, some presenting a 

 mere knife-like edge in cross-section, others being stout and 

 thickened, up to as much as two millimetres. 



The surface, where exposed in the round, seems to be quite 

 devoid of sculpture. The tube walls are composed of calcedony, 

 with here and there a calcite infilling. It follows that great 

 alteration and replacement must have gone on subsequent to the 

 original foss-ilisation ; this is borne out V)y the condition of the 

 wood, to be referred to later. The late Dr. Gwyn Jeffreys says' 

 the sheath or tube of Teredo in the recent state is destitute of 

 anything like true structure, and only composed of minute cal- 

 careous particles agglutinated together. In the great Kufhus 

 arenarius, on the other hand, the sheath exhibits a prismatic 

 crystalline structure, and in a figure given by Mr. J. Griffith* the 

 prisms are seen to be arranged in concentric rings. Dr. G. Johnston 

 says^ the prisms are short and perpendicular to the surface. 



Similar large Teredo-\\ke tubes have been described from Creta- 

 ceous rocks. Stoliczka figures one, T. crassula,^'^ from the Ootatoor 



6 Griffith -Phil. Trans, for 1806, pt 2, p. 270. 

 ^ Jeffreys— Brit. Conchol., iii., 18(55, p. 156. 



8 Griffith — hoc. cit., pi. x., tig. 4. 



9 Johnston- Introd. to Conchol., 1850, p. 431. 



10 Stoliczka — Pal. Indica : Cretaceous Fauna S. India, iii., pts. 1-4, 1870, 

 p. 16, pi. i., f. 2. 



