[ ii8 ] 

 PERFORATIONS IN CARBONIFEROUS I.IMESTONE. 



BY R. F. SCHARFF, PH.D., B.SC. 



I HAVF been asked by Mr. Carpenter to make a few obser- 

 vations on the very remarkable perforations which Mr. Owen 

 Smith discovered in the Carboniferous lyimestone near 

 Nobber, Co. Meath. They were first described by him in 

 the June number of the Irish Naturalist, and the following 

 month notes appeared by Messrs. Fallon, McBride, and 

 Walpole, w^ho had all seen similar perforated rocks in different 

 parts of the countr3^ The Rev. Mr. Close has also observed 

 them by the side of Lough Mask, and he remarks that we 

 have to choose between the only two alternatives: — that 

 these perforations have been produced by weathering or by 

 the action of a boring mollusc. Mr. Smith is in favour of the 

 latter view, but most of the writers of the above-mentioned 

 notes are rather in favour of their having been caused by the 

 action of water on the limestone. 



But when we consider the position of the holes, their 

 var3dng depth while the diameter remains constant, their 

 upward tendency, their being confined to a portion of the 

 stone only, and, as Mr. Smith justly remarks, their great 

 "family likeness," the aqueous theory presents formidable 

 difiiculties. Indeed it seems to me impossible to conceive 

 how either chemical or mechanical action of water could 

 produce these perfectly smooth perforations of an inch in 

 diameter on the face of a limestone rock, and having seen the 

 specimen which was forwarded to the Editors of the Irish 

 Naturalist, I have not a doubt that the explanation given 

 by Mr. Smith is the correct one. 



A marine boring mollusc {Pholas crispata), still inhabiting 

 the Irish Sea, fits exactly into some of the holes, and the 

 first impulse to attribute the perforations to the action of this 

 or an allied species appears quite justified. The geological 

 deductions, moreover, w^hich we can draw from such a con- 

 clusion are so seductive that it is difficult to abandon a theory 

 of such important bearings. Pholas-borings m sihc at 

 Nobber, in such a fresh condition, mean that within very 

 recent times that locality must have been covered by the sea, 

 perhaps to a depth of 200 feet, for the species of Pholas are 

 known to live at a depth below the surface of the sea not 

 exceeding 30 fathoms. We know that marine shells are 

 found at an altitude of about 1000 feet in the Dublin Moun- 

 tains, and the presence of a number of other deposits in 

 various parts of Ireland renders it extremely probable that 

 within a recent geological period the sea covered a large 

 portion of eastern Ireland at any rate. In spite of a number 

 of facts which may be adduced as evidence in support of the 



