EXPLANATION OF PLATE XXI. 



SuRCULA PARVA Coiirad (p. 117). 

 Fig. 1. View of tbe only fiasment. which I have observed, eiilarfjed -'i diameters. 



Uiiii.i.iA Kl.KOANS Emmons (\t. 11.')). 



Figs. 2. View of a fragmeut wbi(-li pieserves ouly the lower voliitiou ami a half. 



3.4. Two views of a iimre peife<t specimen, but still imperfect in the spire. 

 All twice enlarged. 



DrII.MA SlIBl'LEXUDSA Whltf. (]). 110). 

 Figs. 5,6,7. Three views of a very perfect shell, twice enlarged. 



IH:ii,i,i.\ I'.sKUDHBURNEA Hellprin sp. (p. 114). 



Fig. 8. View of a sliort, broad .specimen. 



9, 10. Two views of a more slender form. 

 11, 12. Two views of Prof Heilprin's type specimens. 



All ligiires rather more than twice the natural size. 



Nevkhita DUi'LiCATA Say (p. 121). 



F"IG8. 13, 14. Two views of a nearly entire shell, showing the usual umbilical callosity, twice natural 

 size. 

 15, 16. Two views of another imperfect specimen having the callus extending to the upper 

 margin of the lip, natural size. 



186 



