132 UNIVALVES MUREX. 



The next division comprises those species which are 

 commonly known by the name of Triplices, or more 

 properly Purpurae, as the animals inhabiting most of 

 the shells of this class produce a liquid of a rich purple 

 color, hence the whole genus has by some authors 

 been called Purpura: the species are foliated, and 

 have a much shorter beak than those of the preceding. 

 The sutures are composed of crisped foliations, and 

 acute angular ramifications, which are most striking- 

 ly marked in the M. radix, and the pink and yellow 

 mouthed varieties of the M. saxatilis. The number of 

 rows in these sutures differs considerably, some, as 

 the M. ramosus, &c. have but three, the M. scorpio 

 has four, and the M. saxatilis five. 



The fourth division is composed of those species that 

 have their sutures thick, protuberant, and rounded ; such 

 are the M. rana, M. femorale (or Gadroon-whelk) 

 and M. lyratus. The fifth division consists of only two 

 species, which are of irregular form. 



In the species of the sixth division, the form is more 

 abbreviated and gibbous, they are also more or less 

 spinous, and without a manifest beak : as the M. rici- 

 nus, M. hippocastanum, M. neritoideus. 



The nintli division is composed of such shells as have 

 a long, straight, subulate, closed beak, and unarmed 

 with spines. The M. babylonius, and others of the first 

 family, have a small fissure or incision on the extremity 

 of the outer lip, close to the termination of the 

 first whorl, a peculiarity solely confined to these 

 species. 



