244 PROCEEDINGS OF THE NATIONAL MUSEUM Vol.89 



Subfamily Annulariinae Henderson and Bartsch 

 1920. Annularinae Henderson and Bartsch, Proc. U. S. Nat. Mus., vol. 58, p. 71. 



Shell ranging in form from depressed-lielicoid to elongate-conic. The 

 axial sculpture may be almost obsolete or it may consist of strong ribs 

 or many slender lamellae, which may or may not be gathered mto tufts 

 at the summit. The spiral sculpture may be absent, confined to the 

 umbilicus, or cover spire and base. In strength the spiral sculpture 

 varies from fine threads to strong cords. Breathing devices are 

 present in some groups and absent in others. They range from a 

 mere notch or slit puncture to a pore with external siphon. The 

 operculum may be flat or convex on the outside, provided with a 

 calcified lamella, which rises from the inner edge of the whorls. This 

 lamella may be vertically placed upon the basal plate or it may be 

 obliquely situated or reflected to parallel the basal plate. It may 

 be almost smooth or ribbed. 



Type genus. — Annularia Schumacher. 



KEY TO THE GENERA OF THE SUBFAMmY ANNULARIINAE 



Outer edge of the opercular lamella touching that of the succeeding whorl, thus 

 forming a continuous surface. 

 Nuclear whorls thimble-pitted. 



Nuclear whorls with axial ribs and spiral threads Limadorez 



Nuclear whorls without axial ribs or spiral threads Limadora 



Nuclear whorls not thimble-pitted. 



Nuclear whorls microscopically granulose Tudora 



Outer edge of the opercular lamella not touching that of the succeed- 

 ing whorl, thus not forming a continuous surface Annularia 



LIMADOREX, new genus 



Small tudorids having the nuclear whorls thimble-pitted and in 

 addition provided with axial riblets and spiral threads, which char- 

 acters at once distinguish it from Limadora. The postnuclear whorls 

 are marked by sublamellar, wavy axial ribs. Peristome double. 

 Breathing puncture present. 



Type : Limadorex limonensis, new species. 



LIMADOREX LIMONENSIS, new species 



Plate 22, Figures 6, 7 

 Shell rather large, elongate-conic, pale yellow. Nuclear whorls 2, 

 strongly rounded, with the first whorl showing indications of retrac- 

 tively slanting axial ribs and with the entire surface thimble-pitted. 

 Postnuclear whorls inflated, strongly rounded, marked by slightly 

 retractively slanting axial riblets, of which 102 occur on the first of the 

 remaining turns, 138 on the second, and 158 on the last. These rib- 

 lets are not quite so wide as the spaces that separate them, and they 

 are expanded at the summit and at the periphery into more or less 

 auricular elements, which are usually fused. The spiral sculpture con- 



