160 Mr. W. Thompson on Chelura terebrans. 



Lamarck, t. vi. p. 47 (1835), quotes only Turton and Sowerby's 

 ' Genera of Shells * (no. 29. tab. 101) :— he calls it Pholas xylo- 

 phaga. Broderip too in the ' Penny Cyclopaedia ' brings it under 

 the genus Pholas, figures it in the wood, and also represents the 

 valves separately and joined. It is there noticed as " found in 

 cylindrical cavities eaten ? in wood," but certainly there is no 

 doubt, as there indicated, of its being the real excavator of the 

 burrows it inhabits. Philippi does not include this species in 

 either of his volumes on the Mollusca of the Two Sicilies ; but 

 it appears in the very lately published ' Index Molluscorum 

 Scandinavia? ? of Loven : — this author refers only to Turton and 

 Deshayes for it : he notices it simply as found in Norway. 



This species differs from Teredo navalis, Turt., by boring 

 against the grain of the wood (all of which is pine), in a diagonal 

 manner. 



Within a few square inches of this wood, the perforations of 

 both these species may be seen : they labour harmoniously to- 

 gether in the work of destruction, the one destroying the timber 

 by boring it in a longitudinal direction, the other by its opera- 

 tions being directed against the grain. They both work within 

 the outer surface of the wood, but this again is destroyed from 

 without inwards by the Limnoria and Chelura. Many of the 

 chambers of the Xylophaga before me are 1J inch in length, 

 thus exceeding by one half the longest noticed by Turton. The 

 shells of my largest specimens are 5|- lines in length : the two 

 valves joined at the hinge occupy a space of 5^ lines in diameter. 



Specimens obtained in rotten timber in 1828 at Bingsend, 

 Dublin bay, by W. H. Harvey, Esq., have been given to me by 

 that gentleman, and when in Dublin in March last I saw in 

 Mr. Warren's collection a piece of wood (sound) filled with the 

 perforations and valves of this species, of which latter I was 

 kindly permitted to take specimens. The wood was found by 

 Mr. Warren on the Dublin coast, where I have little doubt that 

 the species is committing some injury, although such may not yet 

 have been noticed. 



Chelura terebrans, Philippi*. 



All that has been published on this species has already ap- 

 peared in the ' Annals f Philippics paper, in which it was first 

 described, having been translated and republished in the fourth 

 volume ; and Professor Allman's, introducing it as an inhabitant 

 of the British seas, having a place in the Number for the month 



* Professor Allman points out certain trivial differences between the spe- 

 cimens described by Philippi and those from Dublin bay. The latter are 

 similar to those from Ardrossan, except in size. 



