CHAP. IV. 



DIVISIONS OF THE MITRES. 



129 



genera of the volutes _; and they may be thus briefly 



characterised from their 

 ,^Ssa^^*^^:'.-6^^^ shells. The most typi- 

 cal is — 1 . Mitra,v;here 

 the basal whorl is some- 

 what ventricose, and the 

 aperture has no inter- 

 nal groove. 2. Tiara 

 (fig. 14.) J having the 

 basal whorl contracted, 

 and the internal groove distinct; — this is the sub-typical 

 genus. The 3d, or next, Mitrella, resembles the olives 

 in being smooth, and in having the base of the pillar 

 thickened, with the plaits very much projecting. In 

 the 4th, or Conoehelijc, the spire is very short, the plaits 

 numerous, and sometimes indistinct: whereas, in the 5th, 

 or Mitreola, the upper plaits are smallest, the outer lip 

 inflected and sometimes toothed, and the spire slightly 

 papillary. As all these peculiarities will be detailed in 

 the next division of our volume, we shall here only make 

 a few general observations on the contents of the genera ; 

 and first, with regard to 



The Analogies of the Volutins and the Mitring. 



Genera of the 

 MitrincB. 



MiTRA. 



Tiara. 



Mitreola. 



CONfEHELIX. 



Mitrella. 



■\ 



Analogical Characters. 



rBody-wliorl never contracted at 

 < the base ; the whorls never tur 

 C retedor anguiated. 



fShell turreted; body-whorl con-~| 

 I traded in the middle; the] 

 <{ whorls nodulous or sub-coro- J* 

 I nated, or carinated, larely | 

 L smooth. J 



rThe upper plaits on the pillar^ 

 -5 smaller than those in the mid- v 

 C die ; spire sometimes papillary. J 

 Spire very short; plaits very slen- ^ 

 der, sometimes obsolete ; sur- f 

 face generally reticulated or f 

 striated. 3 



r Smooth, generally polished; the"^ 

 -< lower plaits smaller than the > 

 C upper. 3 



Genera of the 

 Volutince. 



V GLUT a. 



Cymbiola. 



Harpula. 



Volutilithes. 



SCAPHELI.A. 



K 



