260 



J. G. WALLER ON CLIONA CELATA, ETC. 



I now return to the mode of operation, and the forms resulting in 

 these excavations, because, as such forms are never absent, they 

 constitute a test, the determination of which must settle all con- 

 troversy on this subject. I refer you to a drawing from a section of 

 oyster-shell in my possession. (PI. XXI, Fig. 1.) Here you get the 

 sub-circular contiguous hollows, to which I have before alluded, and 

 also an elongated channel diminishing as it proceeds. All these are 

 excavated precisely upon the same principle of sub-circular excava- 

 tions, whether they be large or small. I must specially direct your 

 attention to the manner in which these are made, and to the 

 certainty, that they are each excavated separately. Let us suppose 

 one circle made first, another added, encroaching upon its boundary, 

 in a more or less degree, and we find the problem of the work deter- 

 mined. The sharp clear outlines of this operation point inevitably 

 to a hard tool as the factor. The smaller ones differ only as sucli, 

 and can be accounted for only in the same manner.* (!See PL XX, 

 Figs. 7, 8, 9, 10.) 



In all microscopic work measurements are of great value. These 

 sub-circular depressions, in the larger normal size, average the 

 500th of an inch in diameter, and the smallest diameter of an 

 elongated channel is the 2,000th of an inch ; I have met with no 

 excavation smaller than this. I may again refer to these measure- 

 ments. 



I now call your attention to this pebble of limestone. Some years 

 ago, during a stay of two months at Torquay, closely engaged all 

 day during the week, I, one morning on the day of rest, walked to 

 Babbicombe bay. The morning was lovely — it was at summer's close 

 — the sea was as calm as a mill dam, its blue-green colour 

 emulated that of the Mediterranean, whilst the soft air of Devon- 

 shire might almost carry you to the sunny south. Add to this, the 

 rich colour of the New Red Sandstone cliffs, as tilted by upheaval, 

 they lay on the flanks of the limestone with masses of luxuriant 

 vegetation around, and there was a noble picture for the eye to rest 

 on, and to give the jaded mind repose. Thus I descended to the 

 shore, the tide running out, to listen to ** sermons in stones." 



The limestone boulders here, as in other parts of this coast, 

 exhibit the excavations of an Annelid, which, I believe, is well- 

 known. But, at dead low water, I made my observations rather on 



* Since writirp this, I find this character of the work did not escape the 

 vigilance of Dr. Bowtibank, who alludes to it in Vol. ii., p. 220. 



