162 J. Starkie Gardner — Teredo in the Eocene. 



destroyed than when the true ship-worm has been at work. 1 Some- 

 thing- very like it is present in the Chalk ; but when we come to the 

 Eocenes, there is no longer any possibility of doubt as to the animal 

 which has made its home in the drifting logs, for they are riddled in 

 the way peculiar to the true ship-worm, and its shell is frequently 

 left in the bore-holes. The distribution of such bored wood in our 

 Eocenes must prove very instructive in many ways, when the habits 

 of the living animal are more thoroughly known. As far as my 

 own observations go, it occurs in the following beds, but I trust many 

 of our numerous local observers will contribute additional and more 

 precise information. 



Thanet Beds. — A good deal of the silicified wood from the Thanet 

 series of Heme Bay is bored by Teredo. Mr. Dowker, F.G.S., 

 observes that most of the perforations are parallel with the grain of 

 the wood, and mostly range from ■&■ to -fy of an inch in diameter, 

 though there are many smaller bores associated with them. 



Beading Beds. — I have no recollection of meeting with Teredo- 

 bored wood in this formation. 



Woolwich Beds. — Teredo has been recorded from Charlton and 

 Sunderidge. It is probable that all wood from these deposits will 

 prove to be bored by the ship-worm. 



Oldhaven Beds. — Teredo is recorded by Mr.Whitaker from Charlton, 

 Sunderidge, and Eeculvers. 



London Clay. — In reply to my inquiry, Mr.W. H. Shrubsole, F.G.S., 

 has very kindly sent me a response which I cannot do better than 

 quote : — 



" Of the very large number of fossil trunks that I have observed, 

 in nearly every case, if not in all, it has been evident that the Teredo 

 borings were on one side of the ovally compressed stem, and in 

 every instance where I have examined these trunks in situ, either in 

 the cliff or on the undisturbed clay floor of the foreshore, I have 

 found the borings only on the underside. This seems to show that 

 the Teredo attacked the log when it was floating at the surface, and 

 that it was silted up very soon after becoming water-logged and 

 going to the bottom. 



" The upper surface generally has a limestone covering some 

 inches in thickness. The trunks are nearly always cracked up into 

 lengths varying from two to four feet. It is extremely rare 

 to find a log, large or small, that has not been bored. I have just 

 examined a segment of a large fossil trunk which I selected and 

 brought home as being less mutilated by Teredo than any I had seen 

 for a long time, and I find that its appearance quite supports the 

 statement made above. 



" Another segment of the same trunk I had cut up transversely 

 into slabs. One of these slabs (polished) is at Jermyn Street, and 

 another, I think, at Cromwell Boad Museum. Eeference to them 

 will probably show that owing to destructive action on one side the 

 natural axis is eccentric. 



1 Teredo lias been recorded from the Jurassics, but the generic identity is, I think, 

 doubtful. 



