388 



Murex, Triton, and Ranella have always been associated together 

 as members of one family by universal consent, and it must be con- 

 fessed that the external resemblance between them is very remark- 

 able ; but on comparing the lingual and labial dental organs of Triton 

 or Ranella with those of Murex, it will be at once perceived that the 

 latter genus can have no immediate affinity with either of the former 

 genera. 



The aperture of the proboscis in Murex is transverse, and armed 

 with two horizontally arranged dental plates, connected laterally by 

 the minute semi-calcified cells which line this part. The upper plate 

 presents a rough palatal surface, with an anterior encrusted cutting 

 border, much resembling that of the crescentic mandible of Limax 

 or Helix ; whereas the dental plates of Triton and Ranella consist 

 of oblique rhombic cells identical in character with those of Cyclo- 

 phorus or Natica, disposed laterally. Again, on comparing the 

 lingual strap of Murex with that of Triton or Ranella, we remark, 

 first, that each transverse row of the former consists of three mem- 

 bers, viz. one in the rachis, and one in each pleura, while in the two 

 latter cases the pleurae present two additional elements ; thus there 

 are seven series of dental plates in the strap. The tongue-strap of 

 Murex, moreover, is lengthy like that of Purpura and Ricinula, both 

 of which genera are more closely allied to Murex than perhaps any 

 others referred to its family. 



The strap of Triton and Ranella, on the other hand, is compara- 

 tively much shorter, and singularly enough more nearly approaches 

 that of Pileopsis or Vermetus, not only in general proportions, but 

 also in the actual number and configuration of the dental plates and 

 processes. Now with these facts before us, it will be scarcely worth 

 while entering further into the characters of the lingual dentition 

 of Murex, Triton, and Ranella, but the most superficial exami- 

 nation of the figures (which accompany the communication) will 

 show that Murex must be separated from its assumed alliance with 

 Triton and Ranella, while the close relationship of the two latter 

 genera gains additional support. 



On comparing the lingual dentition of the genus Cyrtulus with 

 that of Tritonidea of Swainson (the Polia of Gray), both are found 

 to be naturally allied by characters which very distinctly manifest 

 a family relationship, and Swaiuson's genus Muncidea, with several 



