CHAPTER II: THE MUREX SHELLS. ROCK 



SHELLS 



Family Muricid^ 



Shell spiral, fusiform, with anterior canal or notch; whorls 

 thickened by varices or nodules at each rest period of growth; 

 aperture roundish; operculum horny; mantle enclosed, with 

 ruffled border whose extension lines anterior canal; foot broad, 

 simple; eyes present; branchial plumes, two; radula long, slim, 

 with teeth in three series; sexes distinct. 



A large family of marine carnivorous mollusks of high or- 

 ganisation, which creep and swim, chiefly in warm seas. 



The family Muricid^e is divided by Tryon into two sub- 

 families; I. Muricince, adorned with varices, having the nucleus 

 of the operculum near the centre; II. Purpurince, with nodules 

 instead of varices, and with the nucleus of the operculum near 

 the margin. 



The genus Murex overshadows all the others in size, elabor- 

 ateness of decoration, and number of species. 



Sub-family MURICIN^ 

 Genus MUREX, Linn. 



Shell solid, or pear-shaped, with three prominent spiny 

 or branching varices crossing each whorl, and intermediate ones 

 of smaller size. Canal variable in length, partially closed. About 

 two hundred and fifty species, living from low water to fifty 

 fathoms or more, mostly on tropical or sub-tropical shores of both 

 hemispheres. 



The rock shells are distinguished by the striking ornamen- 

 tation of their whorls by spiny processes. Each varix marks the 

 end of a period of growth, when a barricade is built to guard the 

 temporarily closed doorway. The presence of many secondary 



27 



