34 NATUKAL HISTOKY BULLETIN 



EXPLANATION OF PLATE I 



I. SUCCINEA AVITTERI n. S. 



Six shells showing three views. Coralville, Iowa. 



II-III. SUCCINEA AVITTERI D. S. 



Twelve shells showing three views. Iowa City, Iowa. 

 IV. SucciNEA wiTTERi n. s., — jaw. 

 V. SucciNEA wiTTERi n. s., — teeth from radiila. 



a. Central. 



b. First lateral. 



c. First marginal. The tenth and eleventh rows from the cen- 



tral, which usually form the first and second rows of 

 marginals, often have some teeth with but one lateral cusp 

 (hence like laterals) and some M-ith two lateral cusps of 

 the usual inner marginal type. 



d. Seventh marginal, showing three lateral cusps. 



For comparison the following species of Succinea, occurring in Iowa, are 

 figured on the plate: 



VI. Succinea ovalis Say. Three views. Iowa City, Iowa. 

 VII. Succinea retusa Lea. Three views. Iowa City, Iowa. 

 VIII. Succinea ovalis Say. Three views of a variety from yellow loess. 

 Iowa City, Iowa. 

 IX. Succinea grosvenorii Lea. Three views. Hamburg, Iowa. 

 X. Succinea avara Say. Fossil, from yellow loess. Iowa City, Iowa. 

 XL Succinea avara Say. Modern, Eock Eapids, Iowa. 



