30 AMERICAN JOURNAL 



half of the fourth lateral tooth and the fifth lateral tooth. It is 

 taken from a photograph, for which we are indebted to our friend 

 Mr. Sam. Powel, of Newport, R. I. 



There is considerable variation in the shape of this fifth lateral 

 tooth. In some cases the upper margin is excavated along 

 three-fourths of its length. 



Explanation of Plate 2, illustrating the articles by Messrs. Bland 



and Binney. 



Figure 1. Clausilia tridens, Chemn. Three lateral teeth, 

 about the eleventh, twelfth and thirteenth on the right of the 

 central line. These are given to illustrate the passage from the 

 laterals into the marginals. 



Figure 2. Clausilia tridens. The seventh and eighteenth 

 teeth on the right of the central line. These are fully developed 

 marginals. 



Figure 3. Clausilia tridens. The first lateral on the left of 

 the central line. 



Figure 4. Clausilia tridens. The jaw. 



Figure 5. Clausilia tridens. The twelfth lateral on the left 

 of the central line. Compare with figure 1 from another trans- 

 verse series of the same lingual membrane. 



Figure 6. Helicina occulta, Say. The fifth lateral tooth, with 

 a portion of the fourth lateral, to show its basal extension. 



Figure 7. Clausilia tridens. The fifth lateral to the left of 

 the median line. 



Figure 8. Clausilia tridens. The central tooth with the ad- 

 jacent laterals. 



