GASTROPODA— NATICOPSIDJS.. 



675 



ovate ; surface with numerous revolving rows of small tubercles 

 increasing in size with the whorls. 



FlG. 937. Trachydomia prce ursor. (After Clarke. ) 



Coal measures of Indiana, Illinois, Iowa, Missouri, and New 

 Mexico. 

 217. T. nodosum M. and W. (Fig. 939.) Carbonic. 



Fig. 938. Trachydomia wheeleri. ( After Fig. 939. Trachydomia nodosum. 



White, 13th Ind.) (After Meek and Worthen, 111. Pal., II.) 



Larger, more rapidly enlarging, nodes irregularly scattered or 

 arranged in vertical instead of horizontal rows. 

 Coal measures of Ohio, Illinois, and Missouri. 



LXX. Turbonopsis* Grabau and Shimer. 

 Young shell as in Naticopsis ; adult whorls expanding; with 

 wrinkles or ribs, and a median carina. Devonic. 



v&$itev 



Fig. 940. Turbonopsis shumardi, young and adult, X %• (After Hall, Pal. N 



Y.,V.) 



