TURRITELLA. 



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TESTA turrita, spira plerimique elongata : aper-^ 

 turd rotundata, integra, (marginihus supernd 

 disjunctis;) labio externo sinu emarginato, basi 

 interna subcanaliciilata. Operculum orbieiilare, 



, eorneum. 



Separated by Lamarck from the Liiinean Turhines, on 

 account of the generaUy elongated form of the TurriteUa 

 and the sinus in their outer lip. The characters of the aper-. 

 ture are also sufficient to distinguish them from Lamarck's 

 Terebra and Cerithium, (a part of the Linnean genera Buc- 

 cinum and Murex,) which they very much resemble in their 

 general form, and to which, we believe, they are more 

 nearly related than Lamarck seems to think; for, on the 

 one hand, we think we can perceive an evident transition 

 from the Scalarice to the Turritellce; and on the other, 

 from the Turritellce to the Cerithia and Terebrw: we are 

 not, therefore, surprized, that former Conchologists should 

 have classed the Avhole together under the name of Screiu 

 Shells, although there is, indeed, a considerable difference 

 in the form of their apertures. 



The Turritellse are marine shells, w^hose animal is 

 furnished with an orbicular, horny operculum; their spire 

 is more or less turriculate, sometimes consisting of a great 

 number of volutions and very much elongated; the greater 

 number of species are externally furnished with numerous 

 strise or ridges, and the lower part of the volutions in some 

 is strongly carinated, so as to be wider than the next vo- 

 lutions, and to hang over them like the eaves of an house; - 

 but they are not known to have either vertical ribs, nor 

 varices, nor spinose tubercles. Aperture circular, entire, 

 its edges (disunited above) not reflected; outer lip with a 

 more or less deep sinus, generally near the upper part, 

 which; on account of various accidents, is not always dis-. 



