POLYTROPA. 173 



took two days to get through the shell of a moderate-sized 

 mussel.* It does not appear that the prey is destroyed by any 

 poisonous secretion of the whelk, after it has gained access to 

 the interior. The proboscis is at first thrust into the hole which 

 it had drilled, and the whelk eats in that way ; but when, from the 

 death of the mussel or limpet, the former gapes or the latter 

 separates from the rock, the l^irptira devours the remainder by 

 the natural opening. 



"According to Mr. Peach, it deposits its spawn all the year 

 round, but more actively from January to April. Spawn which 

 he collected in January, 1843. was hatched four months after- 

 wards ; he took forty-seven fry from a single capsule. They 

 soon began to assume the peculiar habit of their parents, by 

 getting out of the water, where they would remain for hours, 

 answering to the period of the ebb and flow of the tide." f 



This is one of the species which furnished the dye known as 

 Tyrian Purple to the ancients (see ante. p. 43). Mr. Jeffreys 

 remarks that the liquor contained iu the egg-capsules is also pur- 

 puriferous, and that it tastes like the strongest pepper. The 

 male P. lapillns is longer and more slender than the female, and 

 has a fine, tapering spire, with a plicated but not tubercular 

 throat. In aged specimens the throat has not unfrequently a 

 succession of tubercular rows, forming internal varices. Occa- 

 sionally the shell is truncated or the first whorls broken and 

 deserted. In brackish water they are smaller and thinner. They 

 are called horsewinMes in Ireland. J 



Like all other predacious and voracious beasts the Purpura 

 meets with retribution occasionally ; here is an instance : 



Mr. Henry Crowther, whilst collecting in the shore pools at 

 Whit by, England, u noticed a commotion amongst the mollusks 



* M. Boucliard-Chantereaux observes that the shells of Purpura lapillus, 

 found on the Boulonnais (France) coast are thinner and smaller in those 

 situations where they are subject to the influence of brackish or fresh 

 water. It is very fond of Mytilus edulu*, Mactra, Donax etc., the shells 

 of which ii bores through in from three to five minutes, preserving per- 

 fect immobility during the operation and protecting the tongue from 

 contact with the sea water by applying the two anterior lobes of its foot 

 closely around its mouth. After boring the shell of its victim, the mantle 

 is torn away, and the viscera only devoured. Jour, de Conch., p. 124, 

 1879. 



f Brit. Couch., iv, 270. J Jeifreys, ibid. 



