Mr. W. Thompson on Teredo norvegica, fyc. 157 



stroy the surface of Casuarina and you render the stem smooth — 

 destroy the surface of Equisetum and you only increase the 

 coarseness and strength of the sulcation. I may also add (in 

 accordance with this view) that age or size has no connexion with 

 this lineation of the surface, as is suggested by M. Brongniart 

 in the last few lines of the quotation from his work at the head 

 of this subject, for I find some of the largest stems perfectly 

 smooth and the smallest occasionally striated. The sheaths are 

 rather coarsely striated, and terminate in thin, flattened leaves, 

 the midrib of which is scarcely discernible. In the weeping or 

 downward curved branches the leaves are completely reflexed so 

 as to point upwards, and according to the position of the stem, 

 are either reflexed, expanded, or lying straight up against the 

 stem. The stems vary from 3 to 7 lines in diameter. 



Common in the white soft shale of Mulubimba, N. S. Wales. 



Phyllotheca Hookeri (M'Coy). PL XI. figs. 4, 5, 6, 7. 

 Sp. Char. Stem simple, coarsely sulcated and ridged longitudi- 

 nally; sheaths very large, loose, subinfundibuliform, each 

 sheath extending from one articulation to the next, so as to 

 conceal the stem ; leaves about twice the length of the sheaths, 

 thick, narrow, and with a strong, prominent midrib. 

 This species is easily known from the two former by its great 

 loose sac-like sheath, completely concealing the stem (see PL XI. 

 figs. 4 & 5), its long, thick, strongly ribbed leaves (see PL XI. 

 fig. 6), and by its stem when stripped of its sheath being coarsely 

 and regularly sulcated, precisely as in the Calamites Cistii (see 

 PL XI. fig. 7). Although abundant, I have never seen a trace 

 of a branch. Some of the flattened stems attain a width of two 

 inches. 



Common in the sandstone of Clark's Hill, in the siliceous 

 schists of Arowa, and in the shales at Mulubimba, N. S. Wales. 



[To be continued.] 



XVI. — Note on the Teredo norvegica (T. navalis, Turton, not 

 Linn.), Xylophaga dorsalis, Limnoria terebrans and Chelura 

 terebrans, combined in destroying the submerged wood-work at 

 the harbour of Ardrossan on the coast of Ayrshire. By Wil- 

 liam Thompson, Esq., Pres. Nat. Hist, and Phil. Society of 

 Belfast*. 



In the Edinburgh" ' Philosophical Journal ' for January 1835, I 

 published a memoir entitled, " On the Teredo navalis and Lim- 



* Read at the Meeting of the British Association at Oxford in June last. 



