APPENDIX TO CHAPTEE XI 



177 



? 2 . Aperture i-f length of shell ; 

 under lip with 2 or more teeth 



c 3 . Non-operculated ; aperture with canal at 

 anterior end ; our species 20 mm. or 



less long 



b 3 . Sinistral ; whorls in contact. 



<"i. Shell ovate-globose, small, not over 5 mm. 

 long, transparent ..... 

 c. 2 . Shell elongated, turreted, slender, less 

 than oO mm. long. .... 

 GS. Shell large, over 100 mm. long, with pro- 

 duced anterior canal . 

 a-2. Shell flat, boat or cup shaped, if somewhat spiral, 



not forming a complete whorl. 

 bi. Shell with apex somewhat spiral and an in- 

 ternal, usually horizontal, partition or dia- 

 phragm 



fto. Shell conical or cup-shaped, with apex turned 



forward ; no shelf or partition. 

 GI. No perforation at apex or notch in mar- 



gin 



c-2. Apex recurved ; margin or apex perfo- 

 rated . . > . . . 



Auriculidce 



(Kx. Mt'lunipiis) 



Triforidce 



Calyptrwidce 



(Ex. Crepidiila) 



Acmceidce 



(Limpets) 



Fissurellidce 



N 



