94 ORDERS AND FAMILIES. 



STENOGYRID^. Shell long, cylindrical, thin, translucent ; spire long, 

 whorls rapidly increasing in size, mouth notched. Achatina, 312. 



SUCCINEID.^. Shell oval or oblong, thin ; spire short, last whorl large, 

 mouth obliquely oval ; tentacles four, retractile. Succinea, 313 to 317. 



TEST ACELLID^;. Animal terrestrial and slug-like ; shell rudimentary, ear- 

 shaped and external, and borne at the posterior end of the body, two 

 pairs of retractile tentacles, eyes at the tip of the upper pair. 

 Testacella, 230, 231. 



Septibranehiata. (PELECYPODA.) Plate xv. Nos. 179 to 183. 



POROMYID^;. Shell small, inequivalve, pearly within ; cartilage in a 

 triangular cavity under each beak ; hinge strong, toothless or not, 

 and having occasionally an ossicle ; foot long and narrow ; siphons 

 short, unequal, separate and surrounded by a tentacular fringe. 

 Poromya, 179; Ne#ra, 180 to 183. 



