PREFACE. 



THE First Part of the present volume treats of the Uro- 

 coptidce, which also formed the subject of Vol. XV. In the 

 determination of species and genera, the keys on pp. xxxi 

 and xxxv should first be consulted. 



It is usually necessary to examine the interior of the shell. 

 In small species, this may be done by rubbing the dorsal side 

 of the shell upon a fine file, or better, a clean oil-stone, until 

 the whole interior is exposed, as in the specimens drawn in 

 pi. 2, figs. 3, 14; pi. 8, fig. 60, etc. In large forms, such as 

 Eucalodium, it is not usually essential that the whole length 

 of the shell be opened. The radula may often be found in 

 shells so opened, coiled closely about the axis. By soaking 

 in warm water it can be removed and mounted in the usual 

 manner. 



The diameter of the shell in this family, as in Clausiliida 

 and others of like contour, is measured across the largest 

 portion of the cylinder, not to the edge of the outer lip, as 

 in Helices and Bulimi. H. A. P. 



(iii) 



