192 NATURAL HISTORY. 



proportion to the diminution of its own size, showing that it must have 

 survived for a considerable time the first closing of its lower 

 end. 



You thus see how little is as yet known of this last discovered species 

 of the genus Teredo. But this scantiness of information and paucity 

 of specimens may be attributed rather to the inaccessibility than to the 

 numerical scarcity of the creature. For an animal that bores several 

 feet deep into a muddy bottom several feet below water cannot be 

 said to offer much encouragement, at least to human beings, to make 

 his acquaintance. But the introduction may in a measure be facilitated 

 if the tubes to be found in such numbers about the Byculla Flats are 

 in fact the remains of this creature. That they are, I think, may 

 be inferred. First, from the similarity of the place in which they 

 are found to that described as the home of Mr. Griffiths' " Sea-worm." 

 At the time when the Indian Ocean ebbed and flowed across the 

 Byculla Flats, their condition must have nearly resembled that of the 

 shallow sheltered bay, with a muddy bottom, in the neighbourhood of 

 Sumatra. Secondly, the general appearance of the shelly tubes here 

 agrees with the descriptions I have quoted to you in every point, 

 except that the structure is concentric instead of radiating, which 

 may be due either to a difference of species or to the alteration the 

 shells have undergone in the process of fossilization.* Thirdly, and 

 most important, we recognise here the longitudinal septum, dividing 

 the tube into two for some inches of its length, which characterized the 

 shells discovered by Mr. Griffiths. 



It is true that in the descriptions and specimens I have mentioned 

 of Kuphus, there are the closed and rounded lower ends which I have 

 not yet succeeded in finding. But these are probably still awaiting 

 discovery some few feet lower down. Major Frere tells me he found 

 one, but I am sorry I never saw it. I have found these two speci- 

 mens, marked No. 7, which at first I was inclined to hope might be 

 the extreme tips of the rounded ends, the shell of which you will 

 remember is described as being very thin. I am however now inclined 

 to think that they are nothing more than the excrescences, which we 

 saw the animal threw out in his shell whenever he changed his direc- 

 tion, and which have been knocked off the tube. I he group of 



* If the process of crystallization were gradual, and the crystal were substituted for the 

 shell in successive layers, hut were afterwards decomposed, say by heat, the structure of 

 the tube would be concentric and the text,ur« non-crystalliue. If tn« h»at were not suffi- 

 cient to penetrate the whole tbirkness of tube, the centre layers would still be crystal- 

 line, &s first altered from the shell, and the outer and inner l on-crystal line, Dot accord- 

 ing to the original structure of the shell, but owing to the second alteration it had under- 

 gone from its crystalline shape. 



