Zoological Society. 383 



the light passes through the membrane, which thus loses its white 

 appearance. When the water escapes from the pores by evapora- 

 tion, or is driven from them by heat, the membrane again reflects 

 white light from the numerous surfaces of its pores. 



" As the colouring matter resides in the shell itself, its peculiar 

 colour is seen through the epidermis as distinctly where it is porous 

 as where it is not porous, when the porous portion has been ren- 

 dered transparent by the absorption of a fluid. 



" If we apply oil or varnish to the white pattern, we may oblite- 

 rate it permanently, or we may change it into a pattern entirely dif- 

 ferent from the original one. 



" If these observations appear to you to have any interest, you 

 are welcome to make any use of them you please. 



" I am, dear Sir, ever most faithfully yours, 



*.* D. Brewster." 



It will be observed, that Sir David Brewster points out how the 

 application of oil or varnish to the white pattern may obliterate it 

 permanently ; such a case has already happened more than once : 

 persons who have become possessed of some of the species whose 

 patterns are lost on immersion, not content with their natural 

 beauties, and unaware of their peculiarity, have had recourse to art, 

 and by applying oil or varnish, have spoiled their specimens, — a 

 proper punishment for trying to mend nature. 



Jan. 26, 1841. — William Yarrell, Esq., Vice-President, in the Chair. 

 A continuation of Mr. G. B. Sowerby's descriptions of new species 

 of shells, collected by H. Cuming, Esq. in the Philippine Islands, 

 was read. 



Helix monochroa. Hel. testd suborbiculari, tenuiusculd, subpal- 

 lescente brunned, hand nitente; spird mediocri ; anfractibus quatuor, 

 ventricosis, rugulosis, ultimo maximo, cteteris multb majori ; fasciis 

 binis mediants saturatioribus, binis pallidioribus ; suturd distincte 

 impressd ; aperturd subelliptico-semilunari, intus alba ; labio ex- 

 terno latiusculo, rotundato-reflexo, extus subfusco ; labio interno 

 tenuissimo, columellari subdilatato, umbilicum mediocrem partim 

 tegente. 

 Long. 1-3, lat. 2' poll. 

 Hab. ad insulam Tablas dictam. 



This species appears to be very distinct from any of those given 

 by De Ferussac, as well as from the Helix Cailliaudi of Deshayes, 

 with which I have compared it. Besides the rugulosities which 

 cover the external surface, oblique lines of growth are easily distin- 

 guishable, which are stronger near the suture. 



Helix chlorochroa. Hel. testd globoso-suborbiculari, tenuiusculd, 

 pallide brunned, haud nitente ; spird elevatiusculd ; anfractibus A\, 

 ventricosis, Icevibus ; striis solum incrementi tenuibus insculptis, ul- 

 timo maximo, ceteris multo majori ; fascid unicd albidd mediand ; 

 suturd distinctd ; aperturd rotundato-sublunari, intus alba ; labio 

 externo rotundato-reflexo, fuscescente, interno tenui ; labio columel- 

 lari lato, albicante; subsinuoso, profunde ineunte ; umbilico nullo. 



