478 MITRICID^E. 



armed with hard parts of variable lengths for boring and 

 sucking their prey. They all have the double branchial plume, 

 mucous fillets, and more or less long branchial fold ; the sto- 

 mach, liver, heart, auricles, ovarium, testis, organe generateur, 

 and nervous ganglia, in short, the entire internal anatomy 

 scarcely differs. The variations are specialties of small value, 

 as the size and outline of the foot and its operculum, the 

 different distances of the pediculated eyes from the base of 

 the tentacula, and the variations in the external markings 

 and contour of the hard parts ; with respect to which we may 

 observe, that they arise solely from the varying disposition of 

 the mucous glands of the mantle, combined with the variety 

 of food and habitat : but we think such differences do not 

 constitute generic distinction. 



Conchologists will ask, if the present numerous genera of 

 this family are merged in the single one of Mureoc, how are 

 they to distribute the multitudinous species ? The only answer 

 is, not by dividing the simple genus into twenty others of 

 similar characters. If the genera of these gentlemen are 

 intended only as aids for the arrangement of vast numbers 

 of species, such symbols might be accepted, though objec- 

 tionable as to appellation, because, without explanation, they 

 would convey ideas of generic distinction rather than of 

 divisional assistance; it is therefore better to consider the 

 variations of form and markings as simple sectional guides 

 to reduce an enormous family to comparatively easy identi- 

 fication of its species. It is a very illogical position, that 

 because a genus happens to have a thousand species or more 

 instead of ten, it is on that account to be cut up into 

 numerous genera, which are absolutely misnomers, being 

 without generic distinction. For these reasons I shall con- 

 sider all the British Canalifera, and such of Lamarck's Pur- 

 purifera as comprise any of our indigena, as represented on 

 malacological grounds by the animal of the ancient genus 

 Murex, dividing the species into specific groups by the marked 

 variations of the forms and sculpture of the shells, and by 

 sectional indices and definitions. 



If, however, malacologists will not dispense with the old 



