Royal Physical Society. 9 



Anatomy of the Porbeagle Shark, Squalus cornubicus. By T. Spencer 

 Cobbold, M.D. From the Author. 3. Literary Papers of the late Pro- 

 fessor Edward Forbes. From Lovell Reeve, Esq., London. 



I. On the Discovery of Diatomacece in the Silurian Slates of Scotland. 

 By Alexander Bryson, Esq. 



In a former paper, read at the last meeting of the Society, Mr Bryson 

 had indicated a hope that Diatoms might be found in the lower Silurian 

 formations of Scotland, from the peculiar appearance resembling organ- 

 isms which he observed in a microscopic section of the slate from Thornie- 

 lee 'Quarry, in Peeblesshire. One form is identical with a rare species 

 found in the guano 'of Ichaboe, both in form and colour. In an endeavour 

 to separate the alumina from the silica in the slate he had met with diffi- 

 culties, as any solvent of alumina also acted on the silica of which he 

 supposed the diatoms to consist. Dr George "Wilson suggested the boil- 

 ing of the powdered slate in Nordhausen sulphuric acid, which was found 

 after a long time to isolate the silica. After many washings of the resi- 

 due with distilled water, the author found several forms of diatomacege, 

 two identical with living species, and four or five quite aberrant. After 

 digestion with nitric acid the organisms seemed fewer, which he referred 

 to their being more horny than silicious. 



II. Notes on a Species of Nostoc or Sky-Jelly (specimen exhibited by 

 Dr Heddle). By Alexander Bryson, Esq. 



III. Description of a New Species of Trematode Worm, with Observa- 

 tions on the Structure of Cercarios. By T. Spencer Cobbold, M.D. 



Specimens of the worm were exhibited. They had been obtained from 

 the liver of a giraffe, and differed from all known species. Dr Cobbold 

 illustrated his paper with numerous drawings, showing the minute ana- 

 tomy of this worm, and also several embryonic forms of entozoa. 



IV. P. A. Dassauville, Esq., exhibited a specimen of the Gray Phala- 

 rope (Phalaropus lobatus, Lath.), which was shot in the Firth of Forth 

 in December last. The bird was only beginning to assume its winter 

 plumage, and appears to be rare in this locality. 



V. Analysis of Datholite from Glen Farg. By M. Forster Heddle, M.D. 



Datholite, Dr Heddle said, had been found in the British islands in 

 four localities, all of these being Scottish — first, by Mr Rose, on the yel- 

 low prehnite of Salisbury Crags ; then at Glen Farg in Perthshire, asso- 

 ciated with zeolites, and well crystallized ; next, upon prehnite, in what 

 is mineralogically called the " Greenockite Hole," namely, the tunnel on 

 the Glasgow and Greenock Railway ; and, lastly, at Corstorphine Hill, 

 by Mr Forrest, within the last few years. It is a fact worth notice, that 

 three out of these four are prehnite localities. This might warrant a 



VOL. I. B 



