Dr. J. E. Gray on the Teeth of t..e Genus Mitra. 129 



XV. — On the Teeth of the Genus Mitra, Lamar cki 'i'^ tx^ 

 By J. E. Gray, Ph.D., F.R.S., V.P.Z.S. &c. 



The greater the number of examples of the different genera of 

 Gasteropodous MoUusca I have been able to examine, the more I 

 am convinced of the importance of the characters afforded by the 

 teeth of these animals, both for arranging the species and genera 

 into natural groups and characterizing them. The general re- 

 sults of my recent observations have been to verify the views I 

 have from time to time published in this Journal on the subject. 

 Within the last few days, however, I have been enabled to exa- 

 mine the teeth of six species of the genus Mitra of Lamarck, and 

 with a very curious result. The teeth of each of the species ai"e 

 very different, and, what is still more extraordinary, they belong 

 to three very different kinds : thus, Mitra Grcenlandica is the only 

 one which has the single rachiglossal tooth of the Volutidce, which 

 is like that of the Cymbiola Turneri in form. 



Mitra episcopalis, M. adusta, M. Ticaonica, and M. cucume- 

 rina, as belonging to the restricted genus Mitra, have three series 

 of odontoglossal teeth like the family Fasciolariada. The broad 

 lateral teeth, which were alone figured by Quoy and Gaimard as 

 the teeth of the genus, are very uniform in shape and struc- 

 ture in the diffei-ent species ; while the central tooth of each offers 

 considerable variation. In Mitra adusta it is narrow, and has 

 only a single, very long, hook -like apex, while in the other spe- 

 cies it is broader, with from five to eight teeth on its upper 

 edge. 



Lastly, Mitra Caffra, which belongs to Montfort's genus Turris, 

 has the three series of hamiglossal teeth of Muricidce and Buc- 

 cinidce. 



This is another striking instance of the impossibility of ar- 

 ranging Gasteropodous Mollusca from the examination of the 

 shell alone. 



The genus Mitra was peculiar before for having some species 

 with a distinct operculum, while the major part of them were 

 without one. Unfortunately I have not yet been able to examine 

 the teeth of an operculated species. 



I may further observe, as connected with the family Volutida, 

 that I have examined the proboscis of Mitra (Cylindra) Dactylus 

 without being able to discover any teeth, but this may have arisen 

 from the bad state of the specimen. The proboscis of this ani- 

 mal differs from the hard, smooth, rigid form of all the other 

 species I have seen, in being of a spongy texture and closely 

 covered with large conical warts externally. 



Marginella [quinqueplicata) has a single rachiglossal series of 



