MITRA. 



form of different individuals of tlie same species is more- 

 over subject to great variation, the spire in some specimens 

 having double the length which it has in others. 



The Mitres have in general an elongated form, and 

 are pointed at the apex; the length of the spire is for the 

 most part greater than that of the aperture; the aperture 

 itself is elongated, longitudinal, notched at the base, and 

 has a very short canal; outer lip generally rather sharp 

 edged, sometimes however it is a little thickened, crenu- 

 lated, and even furnished with a blunt tooth at the upper 

 part w^ithin. Columella plaited, plaits sharp- edged, the 

 inferior ones smaller. A thin, horny epidermis usually 

 covers the outside; we have never seen any operculum. 



The Mitres are for the most part inhabitants of the 

 Seas of w^arm climates, and particularly of the East Indies, 

 which furnish by far the greater number; it is probable 

 that there exist three times as many recent species as are 

 described in books ; many of them are very beautifully 

 coloured, and we may add that tew are common shells. 

 The fossil species are also numerous, they occur in nearly 

 all the tertiary beds. 



With respect to the divisions of the genus, we are 

 not disposed to say much; only we think it will be desir- 

 able, in order to facilitate the discovery of species, to 

 increase the number of divisions, particularly when it is 

 remembered that there are perhaps 250 species : indeed it 

 is almost impossible to ascertain many of the species enu- 

 merated by Lamarck, for want of some indication of his dis- 

 tribution of them: this however is not the only difficulty, 

 for it may be further remarked that out of 80 species enu- 

 merated by Lamarck, there are references to figures of 

 only 52; a fact which shows in a most convincing point of 

 view the little attention that has hitherto been given to 

 specific distinctions, and methodical distribution, as well 

 a« the necessity and use of coloured representations. In 

 our plate we have represented one of each of Mr. Swainson's 

 divisions, together with one of those that he has called 

 Conohelix, and such others as appear to show the great* 

 est variety of characters. — In our work on the Species of 

 Shells, we intend to give coloured graphic illustrations of 

 every species and remarkable variety, trusting that our 

 friends who possess unique specimens will ftUow ws tft^ 

 of them for that purpose* 



