Correspondence — Prof. T. Rupert Jones. 



523 



Mr. Macconocliie obtained, some short time since, numerous speci- 

 mens of a Membranipora from the Post-Tertiary beds (Carse Series) 

 of the River Forth above Stirling. An examination showed that 

 it was closely related to M. Lacroixii, but not quite identical. Ex- 

 amples were forwarded to Prof. Busk, F.R.S., who considers it a new 

 species, and has done me the honour to name it after me. The 

 following is his description: — Ifembranipora Etheridgii, n. sp. — 



" Zogecia disposed in regular quin- 

 cuncial order. Apertures entire, oval 

 or oblong. Border thin, finely granu- 

 lar, unarmed. Each apeilure sur- 

 mounted by a blunt tubercle. At 

 first sight resembles M. Lacroixii, but 

 difi'ers in the perfectly regular dispo- 

 sition of the zo93cia and the presence 

 of the single tubercle above each 

 aperture. This tubercle does not 

 appear ever to present the appearance 

 of an opening. The growth forms 

 lace-like expansions on the surface of 

 shells."" Zoc. and Horizon, Goodie 

 Water, near its junction with the 

 Forth, etc. ; River Forth near Mid Frew, and other localities in the 

 neighbourhood of Kippen, Perthshire, in Carse shelly clays of the 

 Raised Beach series. R. Etheridge, Jun. 



Edinbukgh, Oct. 11, 1876. 



THE "SARSEN STONES." 



Sir, — With reference to the fact of the Sarsden or Sarsen Stones of 

 Berkshire being perforated here and there with numerous vertical 

 root-marks, as mentioned in No. 138 of Geol. Mag., December, 1875, 

 p. 589, permit me to add that I have seen other such specimens since 

 that date, and especially near Marlborough, and at Avebury in Wilt- 

 shire. Among the " Grey Wethers " on the Chalk Down, near the 

 former place, I lately saw some good examples ; and on a visit to 

 Avebury, I particularly noticed that one of the enormous upright 

 Sarsens, standing among the ricks of the farms, abounds with these 

 once perpendicular rootlet-holes, together with numerous horizontal 

 casts of stems and other plants-remains. T. Rupert Jones. 



YoBKTOWN, Sept. 20, 1876. 



FOEMATION" OF EOCK-BASINS. 



Sir, — In respect to the challenge thrown down to me in your last 

 Number by my friend Mr. Hugh Miller, I should have been very 

 well contented to have left my defence in the hands of so able a 

 champion as Mr. Bonney. But lest my silence should be interpreted 

 as indicating a lack of courtesy as well as of courage, I respond to 

 the personal appeal whicli is now made to me. 



If Mr. Miller's article is rightly understood by me, I gather, that 

 while prepared to admit the overwhelming probabilities in favour of 

 the view that the formation of the great Alpine lakes is due to the 



