144 rniversity of Michigan 



PLATE XIV 



The scales represent lengths of 50 microns (.05 mm.). The centrals 

 and 1st laterals are shown in their proper relation to each other; the 

 other teeth are simply oriented in regard to the long axis of the radula. 



Fig. 48. Snccinea gyrata. Radula of a medium-sized specimen from 

 C5c. Central, 1st, 7th, 14th and 21st teeth. The three examples of the 

 14th tooth occur within four, consecutive, transverse rows. 



Fig. 49. Succinea gyrata. Jaw from same specimen. 



Fig. 50. TJiysanopliora vanattai. Radula from A3. Central, 1st, 7th 

 and 14th teeth. 



Fig. 51. Thysanoplwra vanattai. Jaw from same specimen. 



Fig. 52. Drymaeus virgidatus. Radula from Cllc. Central, both 1st, 

 3rd, 28th, 52nd, 54th, 57th and 84th teeth. The hair-line below the scale 

 shows the shape of a transverse row. 



Fig. 53. Neosubidin-a harterti. Radula from Bo. Central, 1st, 7th, 

 14th and 19th teeth. The shapes of the smaller cusps of the outer mar- 

 ginal are, of course, indeterminate, as their diameter is less than half the 

 length of light-waves, so they are only visible as points of light. 



