3346 THE MOLLUSKS OR SHELLFISH 



largest living gastropods, attaining a length of about fourteen inches. It is an 

 inhabitant of the Indian Ocean, and also occurs in the Philippine islands. Another 

 giant is the well-known Fusus proboscidiferus, of which the broadly fusiform shell 

 sometimes attains a length of two feet. It is found on the west and northwest coast 

 of Australia, and on account of the peculiar nucleus of the spire has been placed 

 in a separate genus, Megalatractus. The egg capsules form a cylindrical mass 

 marked with a dozen longitudinal equidistant ridges, and divided off into compart- 

 ments, each compartment containing from twenty to thirty young. When they quit 

 the egg case, they are about an inch in length, and bear no resemblance to the full- 

 grown shell. 



The whelks form the characteristic group of the family Bucdnidce, which 

 also includes a considerable number of other genera, and numerous species. 



The animals usually have a long siphon and a large 

 f ot > more or less square in front and somewhat pointed 

 behind; the head is provided with a pair of tentacles 

 which support the eyes on the outside. The lingual 

 ribbon is well developed, with three rows of pronged 

 teeth, the central with three to six cusps, the laterals 



i f " -IA^_AT^J \ i two or three pronged. The form of the shells is 

 ^ Js variable; some are fusiform, with a distinct anterior 



canal, others ovate, with the canal reduced to a mere 



ROW OF TEETH FROM THE RAD- nQtch AU are provided with a horny O perculum, 



ULA OF (a) Baccinum un- . . , ...,,. , r ,, 



. . ,iv.mr which assumes different forms in the various genera. 

 datum, (0) Murex ennaceus. 



Chrysodomus is essentially a northern or Arctic race, 



and one of the fusiform types with a distinct siphonal canal. C. antiquus, the largest 

 of the British marine gastropods, was also common in the English Crags. Reversed 

 or sinistral specimens were the commonest form in the Red Crag. C. contrarius, found 

 living on the coast of Spain and Portugal, is a closely-allied species. Sipho, Volu- 

 topsis, and Jumala are other northern fusiform groups, which have a few British 

 representatives. The common whelk (B, undatum] is the typical representative of 

 the genus Buctinum, and is such a familiar object that a description of the shell is 

 needless. We may, however, direct attention to the variations existing in this species, 

 these being due to difference of locality, depth, etc. Specimens from deep water 

 have much thinner shells than shallow - water forms, and those found on some 

 parts of the Northumberland coast are remarkable for their solidity. Thousands of 

 bushels of this mollusk are annually consumed in London alone, and as much as 

 sixty thousand dollars has been realized in a year by the whelk fishery off Whit- 

 stable. Whelks are used as bait in the cod fishery. The operculum of this species 

 is roundly ovate, formed of concentric layers, the nucleus being a little eccentric. It 

 is comparatively small, and of no use as a defensive door to the shell. On the coast 

 of Kent and Sussex a race exists, provided with two and sometimes three small 

 opercula, instead of one as usual. It is a peculiarity which apparently has become 

 permanent to some extent, but how it originated is a matter of conjecture. The 

 whelk has a wide geographical range, occurring all over the North Sea to the Nor- 

 wegian coast, as far north as Iceland, and on the east coast of the United States 



