T. zizyphinus. The livid Trochus. 

 Species with strong transverse striae ; colour livid, with 

 undulated streaks of red or brownish carnation. 



T. agglutinans. The agglutinating or Carrier Trochus. 



Species umbilicated, with spire very depressed ; the base 

 much enlarged, and as if excavated by the large projection 

 of the angle of the right edge, which advances much beyond 

 the rounded columellar edge ; generally covered with shells, 

 stones, or coral. 



T. niloticus. The large marble Trochus. 

 Species not umbilicated, conical, with base flat and cir- 

 cular ; the columella twisted ; the aperture very angular. 



