366 PROCEEDINGS OF THE NATIONAL MUSEUM Vol.89 



(A.) Jragilis fragilis in being smaller, in having the axial riblets a 

 little more pronoimced and the base less strongly malleated, and in 

 having the umbilical wall marked by quite apparent spiral threads. 

 The type, U.S.N.M. No. 535603, has 4.5 whorls and measures: 

 Length, 8.2 mm.; greater diameter, 10.3 mm.; lesser diameter, 6.5 

 mm. 



Subgenus Annularella Henderson and Bartsch 



1920. Annularella Henderson and Bartsch, Proc. U. S. Nat. Mus., vol. 58, 



p. 73. 

 1920. Tudorellata Henderson and Bartsch, Proc. U. S. Nat. Mus., vol. 58, 



p. 75. 



Shell helicoid. The axial sculpture consists of strong ribs, between 

 which finer axial threads are present. The spiral sculpture is con- 

 fined to the umbilicus. Operculum typically annularid. 



Type: Annularia (Annularella) yunquensis (Pfeiffer). 



The great amount of material now available for study makes it 

 necessary to combine the subgenus Tudorellata with Annularella. 



KEY TO THE SPECIES OF THE SUBGENUS ANNULARELLA 



Last whorl adnate. 

 Inner lip broad. 



Interstitial axial riblets almost as strong as the heavier ribs. 

 Shell conic. 



Umbilicus broad hendersoni 



Umbilicus narrow romeri 



Shell subglobular cumulata 



Interstitial axial riblets finer than the heavier axial ribs. 

 Shell broadly openly umbilicated. 



Shell red victoris 



Shell not red. 



Shell depressed-helicoid y aterasensis 



Shell conic hesmemanni 



Shell narrowly openly umbilicated arquesi 



Inner lip not broad. 



Spiral threads in umbilicus many pseudalata 



Spiral threads in umbilicus few. 



Shell broadly openly umbilicated holguinensis 



Shell narrowly openly umbilicated yumuriensis 



Last whorl solute. 

 Inner lip broad. 



Fine axial riblets many nipensis 



Fine axial riblets few. 



Spiral threads on umbilical wall few tanamensis 



Spiral threads on umbilical wall many libanoensis 



Inner lip not broad. 



Spiral threads on umbilical wall absent. 



Interstitial axial riblets fine natensoni 



Interstitial axial riblets strong interstitialis 



