78 GENERA OF SHELLS. 



line never compressed ; aperture entire, round- 

 ed, not modified by the penultimate whorl : 

 margins separate above. Columella arcuated, 

 flattened, not truncated at base. Operculum. 



The axis of the shell is generally more inclined than 

 that of the trochus. 



T. marmoratus, imperialis, torquatus, Sarmaticus, cornu- 

 tus, argyrostomus, chrysostonms, radiatus, margaritaceus, 

 setosus, Spenglerianus, petholatus, undulatus, pica, versico- 

 lor, smaragdus, cidaris, diaphanus, rugosus, coronatus, 

 crenulatus, hippocastaneum, muricatus, littoreus, ustulatus, 

 Nicobaricus, neritoides, retusus, rudis, obtusatus, pullus, 

 coerulescens, cancellatus, costatus, irroratus, canaliculatus, 

 palliatus, vestita, obligatus. 



PLANAXIS. Shell ovate, conical, solid ; 

 aperture ovate, sublongitudinal. Columella 

 flat, truncated at base, separated from the outer 

 lip by a narrow sinus. Interior surface of the 

 right magin furrowed or lineated, and a callos- 

 ity running under the summit. 



The planaxis is distinguished from phasianella by 

 the truncation of the columella: it is transversely fur- 

 rowed externally, and generally small in size. 



P. sulcata, undulata. 



PHASIANELLA. Shell oval or conic, solid; 

 aperture ovate, longer than broad, entire; lips 

 separate above, the right sharp, not reflected. 

 Columella smooth, compressed, attenuated at 

 base. Operculum calcareous or horny. 



