488 Rev. T. G. Bonney — Burrows in Limestone Rock. 



at the highest point. (2). They are rarest on surfaces much 

 exposed to prevailing winds, or where the rock approaches to a grit. 

 (3). They usually occur on boulders, or projecting rocks, at no 

 great distance from the surface of the soil ; in not a few cases the 

 turf had actually grown into them. (4). The axis of the burrow 

 usually is not at right angles to the surface of the rock ; often 

 is only inclined at a slight angle to it, so that the burrow commences 

 as a channel (if this be not a natural depression utilised), and sinks 

 gradually into the rock. Frequently it is driven into some slight 

 prominence, as though the burrowing animal had first sheltered 

 itself under the lee of this, and then gradually worked its way 

 deeper into the rock. (5). The burrows are very frequently curved. 

 Sometimes the tangents to the axis at the two extremities, if pro- 

 duced to meet, would include an angle not very much greater 

 than 90"^. (6). Helices, especially H. aspersa, are generally 

 abundant in the neighbourhood of these burrows ; empty shells 

 are common in them, and in the freshest, smoothest, and least 

 weathered of them, I always found a living Helix. (7). The con- 

 striction in the upper part of the burrow, characteristic of perfect 

 Pholas excavations, is generally wanting, and though the burrow 

 sometimes contracts towards the mouth, this is often not quite 

 regular in form ; so that a Helix which would exactly fit the end 

 would be able to quit the burrow. At least, I believe this to have 

 been the case with all that I examined. The ends, also, of the 

 burrows are, I think, generally rather flatter than is usual with 

 Pholas holes. 



From the above considerations, and especially from the position of 

 the cavities in the second example described above, the conclusion is, 

 I think, irresistible, that these are not the weathered burrows of 

 departed Pholades, but have been and are being hollowed out by 

 Helices, the principal, if not the only agent being H. aspersa. 



I may, perhaps, in conclusion, be allowed to advert to two other 

 points of my paper, which have been criticized by Mr. Darbishire. 

 (1). The shells found about the sand pit at Gwyfyd farm. (2). The 

 mussel beds exposed in the sand cliffs in Conway Bay ; both of which 

 he considers to have been brought to their present sites by the hand 

 of man. 



The former deposit being now nearly exhausted, I could obtain no 

 fresh evidence as to its age. "When writing, I did not overlook the 

 possibility, strengthened by proximity to the fortress on Pen-y- 

 Dinas, of this being a kitchen-midden ; but the condition of the 

 shells, so different from those in the middens on the S.W. face of 

 the mountain, their comparative rarity, the way in which they were 

 mixed up in the red clay, and the " lie " of the neighbourhood, made 

 me then, as now, think it possible that they had been deposited 

 under water. The latter deposits I have re-examined. On the for- 

 mer occasion I was quite aware of the existence of mussel fisheries in 

 that neighbourhood, and at first attributed these beds to them, but 

 the number of instances in which (in one bed especially) I found 

 both valves in contact, certain indications of a raised beach, and the 



