BY T. STEEL. 443 



Lime (CaO) 12.07 



Carbonate of lime (CaCOs) 71.08 



Sulphate of lime (CaS04) 1.05 



Carbonate of magnesia (MgCOs) Trace 



Alumina and iron oxide (AI2O3 and FeoOs ) 0.80 



Sodium chloride (NaCl) 2.06 



Phosphoric o.xide (P2O5) Trace 



Silica (Si02) 0.35 



Sand 0.24 



Water .. .. 12.35 



100.00 

 III. Shell op Helix aspera. 

 In Australia the shells of this common introduced European garden .snail 

 are notably smaller and thinner than is the case under the more rigorous con- 

 ditions of their native habitat. So far as I have observed in various parts of 

 Australia and about Auckland, New Zealand, the prevailing type of shell agrees 

 precisely with the form described as H. aspera var. tenuior Shuttl. (J. W. 

 Taylor, Monog. Land and Fresh Water Mollusea of British Isles. Part xxiii., 

 Helicidae). 



Not having seen any account of the composition of the shell, I made an 

 examination of examples collected near Sydney. Incidentally it was noticed that 

 when pulverised in the mortar the shells were exceedingly hard and tough and 

 difficult to reduce to a fine powder. Incineration in the course of the analysis 

 had to be conducted very slowly and cautiously owing to the persistent decrepi- 

 tation, even when finely powdered. Before grinding, the shells were well washed 

 and thoroughly air-dried. 



The figures obtained by analysis were: — 



Lime (CaO) 54.00 Calcic carbonate (CaCOs) ■■ .. 91.45 



Phosphoric oxide (P2O5) .. ..... 004 Calcic phosphate (CasPoOs) .... 0.09 



Carbon dioxide (CO2) \ . 40.24 Lime in organic combination ... 2.74 



SiUca (Si02) 0.10 Silica 0.10 



Conchiolin * 5.00 Conchiolin 5.00 



Water 0.62 Water 0-62 



100.00 100.00 



'Containing nitrogen 0.45 



The organic constituent consists of conchiolin, a substance allied to chitin 

 (Watts' Diet. Chem., i., 1879, p. 1107; also J. A. Thomson. Outlines of Zoology, 

 1892, p. 301). 



Examination of the results in the first column shows that part of the lime 

 is in organic combination, the calculated figures being given in the second column. 



It was a matter of surprise to me to find that the shell contained so small 

 a proportion of the organic constituent. 



Analyses of the shells of some marine mollusea, Crania, Terehratulma and 

 Waldheimia by F. Kunckell (Jour. Chem. Soc. Abs., ii., 1899, p. 313) show 

 results of a similar general character as regards calcic carbonate and organic 

 matter, but differing in the presence of magnesia and calcic sulphate which were 

 absent from the shells of H. aspera. 



IV. Urinary Secretion" of Birds and Reptiles. 



Most people have noticed the white calcareous-looking deposit on the excreta 

 of fowls. Popularly this is commonly supposed to consist of excess lime not re- 



