Murex.] GASTROPODA. 399 



tooth transverse and few cusps ; lateral teeth unicuspidate ; formula, 

 as a rule, 1+^+1. 



Shell with a moderately long spire, fusiform, canal more of less 

 elongated, often closed by the approachment of the opposite margins : 

 ornamented with ribs, often spinose or foliated. Operculum ovate, 

 with subapical or apical nucleus. 



The molluscs composing this family are carnivorous, living on 

 Gastropods and Lamellibranchs, whose shell they pierce with the 

 radula, forming a round hole, through which they insert their long 

 proboscis. 



Fossil. The Muricidce first appear in the Cretaceous. 



KEY TO GENERA. 



A. Shell with spiny or foliaceous varices ; canal almost closed ; oper- 



culum with the nucleus subapical . . . . . . MUREX. 



B. Shell usually with numerous foliated varices or simple ribs, some- 



times the spiral lirae predominating ; canal open ; operculum 



with the nucleus sublateral . . . . . . . . TROPHON. 



C. Shell with tubular spines and projecting hollow tubes between the 



varices ; canal closed ; operculum with the nucleus apical . . TYPHIS. 



Genus 1. MUREX, Linnaeus, 1758. 



Murex, L., Syst. Nat., ed. x, 1758, 746. Type : M. brandaris, L. Bolinus, 

 Pusch, 1837. Rhinacantha, H. and A. Adams, 1853. 



Animal with a large broad foot ; tentacles long and tapering, the 

 eyes situated on the outside, near the end ; proboscis cylindrical, 

 long ; verge long, club-shaped, situated on the right side behind the 

 tentacle. Dentition 1 + i+l; the lateral cusps of the central tooth 

 very large, the next two very small, and the central cusp very large ; 

 lateral teeth with single cusps, long and prong-like. 



Shell ovate or oblong ; spire always prominent ; whorls rounded, 

 crossed by 3 or more spinose or foliated varices ; canal long or 

 short, always distinct, partly open. Operculum ovate, with subapical 

 nucleus. 



Over 300 species are known, inhabiting tropical and temperate 

 seas. 



The purple of the ancients was obtained from M. brandaris and 

 M. trunculus. The pigment is contained in cells of the mantle, is 

 colourless or yellowish, but under the influence of light it turns yellow, 

 green, blue, and then purple. The dye can be fixed upon fibres without 

 the help of a mordant, and the colour is brilliant and solid. 



KEY TO SUBGENERA. 



A. Shell with more than 3 varices, foliated or tubulated ; canal 



curved and short . . . . . . . . . . MURICANTHA. 



B. Shell with 3 fin-like or foliated varices ; canal short and 



varicose . PTEROPURPURA. 



