DUBLIIf WITUKAL HI8T0BT 80CTETT. 146 



FRIDAY EVENING, FEBRUARY 4, 1869. 



William Andeews, M. R. I. A., President, in the Chair. 



The previous Minutes were read and signed. 



The President exhibited specimens of the sepiostaire oi Sepia vulgaritf 

 from the west coast of Ireland, and made some general remarks on the 

 peculiarity of the Fauna of the district, enumerating the various species 

 which had been met there, and were either unknown or rare on the rest 

 of the Irish coast. 



Professor J. R. Kinahan, F. L. S., read a communication — 



ON THE TEACINGS FOEMED ON EECENT EOCK SUEFACES BT PATELLA 

 VULGAEI8 AND OTHEE MOLLUSCS. 



Some time since, my friend, Mr. "W. H. Baily, showed me specimens 

 of markings of a peculiar character which had been sent to him as pos- 

 sibly fossil, but which he had proved to be merely surface-marking, and 

 hence necessarily recent. The peculiar appearance presented by them 

 rendered it a matter of interest to identify them. These were as fol- 

 lows : — a number of narrow, linearly rectangular, light-coloured spaces, 

 apparently raised on a dark red ground, and arranged so as to form a 

 series of radiating lines in one direction, or, when considered only in the 

 transverse direction, exhibiting a series of nearly concentric curves, so 

 that, taken as a whole, they presented a plumose appearance, closely re- 

 sembling the impression of one of the plumose polypifera or polyzoa. 



It was suggested by some that such was indeed their origin, and 

 that the spaces represented the points on which the cells of Lepralia, or 

 some allied polyzoon, had been developed, and from which they had sub- 

 sequently disappeared. This conjecture, although an ingenious one, 

 was unsatisfactory to me, for the following reasons : — First, there is 

 no native polyzoon known which would accurately agree with these 

 marks ; next, the total absence of any trace of coenoecium in the speci- 

 mens, for it seemed highly improbable that, in a surface comprising se- 

 veral square yards, aU trace of the animal, if any had ever existed there, 

 shoiild have disappeared ; next, the cells of the coenoecium, being conti- 

 nuous one with the other, ought to leave markings also accurately con- 

 tinuous in one sheet, whereas the rectangular spaces were all, or nearly 

 all, absolutely distinct, and the surface of the stone between them ge- 

 nerally intact ; and lastly, on subjecting the specimen to a simple test, 

 which I have found invaluable in enabling me to distinguish between 

 mere surface-markings and obscure fossil traces, viz., the placing the 

 stone gently and without agitation in a basin containing a couple of 

 inches of clear water, and, after allowing it time to remain for a short 

 time soaking, Tiewing it through the water under a strong sun-light, I 

 found that the markings totally changed their characters, and presented 

 appearances which were incompatible with their supposed polyzoon 

 origin. Under the action of the water, the markings were seen to be 



