ART. 17 MOLLUSKS FROM WYOMING — EEESIDE AND WEYMOUTH 21 



strong, ending in strong nodes; ventro-lateral facet well defined; 

 marginal nodes blunt and heavy, becoming later high and sharp ; 

 suture with very simple saddles. 



whitei. Whorl somewhat compressed; umbilicus small, one-tenth 

 the diameter; umbilical nodes weak, elongated radially; ribs only 

 moderately strong, ending in moderately strong nodes ; ventro-lateral 

 facet fairly well defined; marginal nodes only moderately high; 

 suture with saddles indented by numerous small marginal lobes. 



" u'/wz^ei "(Kanab, Utah). Whorl somewhat compressed; umbili- 

 cus small, one-tenth the diameter; umbilical nodes lacking at all 

 stages; ribs very weak or inner part of flank, becoming stronger to- 

 wards the periphery and ending in weak nodes; ventro-lateral facet 

 poorly denned; marginal nodes only moderately high; suture with 

 saddles indented by numerous small marginal lobes. 



kanabense. (Known only by very small shells.) Whorl much 

 compressed ; umbilicus small, one-tenth the diameter ; umbilical nodes 

 lacking; ribs weak on umbilical part of flank but visible, becoming 

 stronger towards the periphery and ending in weak nodes; ventro- 

 lateral facet poorly defined ; marginal nodes moderately high ; suture 

 with saddles indented by numerous small marginal lobes. 



irwini. Whorl much compressed ; umbilicus small, one-eighth the 

 diameter ; umbilical nodes lacking at all stages ; ribs lacking on inner 

 part of flank and weak on outer part, ending in obscure nodes ; ventro- 

 lateral facet not defined ; marginal nodes relatively low ; suture with 

 saddles indented by numerous small marginal lobes. 



acGeleratwii. (Known only by very small shells.) Whorl not 

 much compressed ; umbilicus small, one-tenth the diameter ; umbilical 

 nodes lacking; ribs weak on inner part of flank, becoming stronger 

 on outer part and ending in fairly strong nodes ; ventro-lateral facet 

 well defined; marginal nodes apparently blunt, connected by ribs 

 which are not depressed; suture with saddles indented by numerous 

 marginal lobes. 



fontieri. Whorls compressed ; umbilicus small, one-tenth the diam- 

 eter ; umbilical nodes lacking ; ribs very weak near umbilicus, stronger 

 on outer part of flank, ending in very weak nodes; ventro-lateral 

 facet obscure; marginal nodes low; suture seems to have saddles 

 with small marginal lobes. 



dumasi. Whorls not much compressed; umbilicus small, one- 

 eighth the diameter; umbilical nodes lacking; ribs weak on inner 

 part of flank, stronger on outer part, ending in weak nodes ; ventro- 

 lateral facet fairly well defined ; marginal tubercles low but distinct ; 

 suture with saddles divided by small marginal lobes. 



'petrascliecld. Whorl not much compressed; umbilicus moderately 

 wide, one-sixth the diameter; umbilical nodes fairly strong, few in 

 number; ribs fairlv strong, ending in moderately strong nodes; 



