PLATE XXXIX. 



Helix fiuviatilis depressa major, anfractibus quatuor, ex utraque parte 

 circa umbilicum cava. Cornu arietis. Tab. 4. jig. 

 13. Da Costa Br. Conch, p. 60. tab. 4. fig. 13. 



Purpura. S. Cochlea fiuviatilis compressa major. List. Exerc, 

 Anai. 2. p. 59. 



The adult shells of this species are from three quarters of an inch, 

 to an inch and a quarter in diameter ; the colours various, generally 

 brownish or ashen colour, inclining in some to red, in others to yellow; 

 the young shells are whitish and more transparent. 



It is very common in ponds and rivers. The animal is blackish 

 brown, and has two red capillary horns *. 



The Helix Nana, or Dwarf of Pennant, fig. 125, is considered by 

 Da Costa and other conchologists, as a young shell of this species. 



* " This fish emits a fine scarlet humour, if a grain of salt of any kind, or a little 

 pepper or ginger, be put into the mouth of the shell. It emits this fine scarlet humour 

 all the year, especially in April and September. Dr. Lister gives a full account of it. 

 He says, this scarlet humour may be readily got, and in great quantity, if a large 

 parcel of these shells be wrapped up in a cloth bag, sprinkling over it a little salt; then 

 the scarlet liquor will ouze plentifully. The colouring part of this humour immediately 

 subsides, if sprinkled with powdered allum, and the rest of it remains like clear water. 

 The colouring part may be strained through a filtering paper, but the elegance of its 

 colour is lost, and it changes into a dull, unpleasant rusty brown. Moreover, if mixed 

 with vinegar, spirit of wine, deliquated vegetable salts, or common salt dissolved, this; 

 elegant scarlet colour perishes in the same manner as when mixed with allum. Neither 

 can this liquor be kept by itself pure and unmixed; for in vain did the doctor strive to 

 preserve it In narrow mouthed bottles or phials, perfectly well closed, and with oil or 

 honey thrown over it. Thus this colour is of so fugitive a nature, that no acid or 

 astringent has been found sufficient, to preserve the elegance of its tint." 



*' Dr. Lister further recites some observations and experiments he made on this 

 scarlet fluid, to discover whether it was a humour of the body, or to be got by lace- 

 ration or incision, as blood ; a saliva from the throat or stomach ; or a particular hu- 

 rnour contained in certain vessels or parts ; but the nicety and difficulty of the experi- 

 ments rendered it impossible far him to determine, it precisely." Da Costa, page 6i, 62j 



