110 MURICID^. 



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 Pur- 

 pura 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 fortj^-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." — Jef- 

 freys, Brit. Conch., iv, 2Y9. 



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 

 Whitby, England, "noticed a commotion amongst the mollusks 

 which was of too brisk a nature for their well-known and char- 

 acteristic slowness. When the obscuring sands which they had 

 thrown up in the fray had settled, he saw that the shells were 

 principally in the possession of hermit crabs, Avhich, under this 

 guise, were attacking a Purpura lapillus and dragging it from 

 its shell. We caught the whole school at once and transferred 

 them to a collecting-bag ; the shells occupied were Nassa pygmsea, 

 Trochus cinereus, Littorina littorea, three sizes, and a P. lapillus, 

 the sheik of the party, for he was taken red-handed. We pre- 

 sume to think that if their object had not been frustrated, 

 there would have been ere long a mutual exchange of crab's 

 clothing." 



M. Bouchard-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 edulus, 

 Mactra, Donax, etc., the shells of which it bores through in from 

 three to five minutes, preserving perfect 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. Aftfer boring the shell of its victim, the 

 mantle is torn away, and the viscera only devoured. — Jour, de 

 Conch., -p. 124, 1879. 



PURPURA (typical). Shell oblong-oval, last whorl large; spire 

 generally short ; aperture ovate, large with an oblique channel 

 or groove at the fore-part ; columella flattened ; outer lip simple. 



PURPURELLA, Dall. Aperture contracted ; outer lip strongly 

 dentate within ; columella flattened, with one or two distinct 

 spiral ridges upon its centre. — P. columeJlaris, Lam. (xliv, 17). 



TRiBULus, Klein. Spire depressed, whorls simple, the last ven- 



