Quaitcily Journal of Concholo^^y. 393 



U. PUSTUi.ATUS, Lea. Common; Mississippi. \'ariable in form, 

 chestnut witli dark concentric lines: some almost Tree from 

 pustules. 



U. PUSTULOSus, I.ea. Abundant in Mississippi, found also in 

 Cedar and DesMoines; distinguished from pusiulatiis by 

 green on umboncs, this character seem.s to be very constant. 



U. PVRAMiDATU?, Lea. Common; INIississippi. Resembles tn'gonus 



when young. 

 U. RECTUS, Lamarck. Abundant in Mississippi, is also in Cedar 



and DesMoines. Young shells are very beautifully green 



rayed, old nearly black; interior from salmon, rose, to 



white. 13.5 cm. long. 



U. RUBiGixosus, Lea. Very rare; Mississippi, Cedar and Des- 

 Moines. It seems to be very closely related to trigoius, Lea. 



U. SECURis, Lea. Common; Mississippi. The young are very 

 beautiful, light epidermis with radiating black spots. 



U. TRIANGULARIS, Bames. Common; Mississippi. Sexes well 

 marked. 



U. TENUissiMUS, Lea. Rare; Mississiivpi. Very thin and fragile, 

 resembles young gracilis; sexes quite unlike. 



U. TRiGONUS, Lea. Common; Mississippi. Light brown color, 

 inside white to rose, umbones high and cur\ing; thick, 

 somewhat globular, slightly sulcate posteriorly from um- 

 bones to margin. 



U. TUBERCULATUS, Barnes. Common; Mississippi and DesMoines. 

 Young, fine dark green; shell attenuated posteriorly, thickly 

 covered with tubercles. 



U. UiXDULATUs, Barnes. Rare here, abundant at DesMoines. 

 Differs from plicafiis in having more and stronger folds, not 

 so tumid, and umbones scarcely rising above lio-ament. I 

 am not certain it is found here. It is certainly a var. of 

 plicatus, as the latter varies in all the particulars enumerated. 



