206 SELECTED NOTES FROM 



Miss Jarrett must be in error about boring-sponges being found 

 in Silurian Belemnites. The Belemnite is not a shell, but an 

 internal skeleton, and the Belemnitidse do not make their appear- 

 ance in geological time until long after the Silurian period, begin- 

 ning and ending, in fact, with the Secondary. H. F. Parsons. 



Black Background for Mounting Specimens— While using Dr. 

 Dudgeon's pocket Sphygmograph, 1 was greatly struck by the 

 good background produced by holding enamelled paper over the 

 flame of burning camphor until it became coated with soot. 



The tracings of the needle were also very white and well 

 defined. This led me to think that it might be applicable for 

 opaque mounting, and peculiarly suited for mounting many species 

 in numbered spaces on our slide. I tried it and found it to work 

 very well. The following is the process I have found most suc- 

 cessful : — The paper is first gummed to a slip of thin card, and 

 after it is dry held over the flame of burning camphor until the 

 surface is evenly coated. 



I found it tedious to rule each line separately, so I hit on a 

 plan which has proved very successful. I took a paper of pins, 

 and after selecting an even row I gummed it to a glass slip, and 

 fixed a handle to the other side of the slip. By this means I 

 could rule all the parallel lines at one stroke, and by another 

 stroke all the lines at right angles to these, thus dividing the slide 

 into equal spaces. 



The spaces can then be numbered with a mounted needle. A 

 weak solution of shellac in spirit should then be poured over the 

 blackened surface and allowed to dry, when it will be found quite 

 fast. The specimens may then be stuck on in the ordinary way 

 with gum. 



The gum I use is a mixture of equal parts of gum arable and 

 tragacanth dissolved in cold water with a little glycerine, and the 

 whole evaporated in a small ointment-pot and kept dry. A drop 

 of water placed on the surface of the gum will dissolve enough 

 for a slide in a few seconds. This combination neither breaks the 

 specimens nor lets them get loose. S. M. Malcomson. 



Bryozoic Rock, Clifton.— The Bryozoa — or Moss Coral, as 

 they are called by some ; Cilio-branchiate Polypes by others — are 



