172 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



the penultimate turn. In addition to the axial ribs the whorls are 

 marked between the sutures by five strong, narrow, spiral keels 

 which render the intersections of the ribs cuspidate. Sutures well 

 impressed. Periphery and base of the last whorl well roimded, 

 marked by the strong continuations of the axial ribs and five spiral 

 keels, similar to those between the sutures. Aperture pear-shaped; 

 outer lip thin, showing the external sculpture within; columella 

 strongly curved and revolute, provided with a v/eak fold at its 

 insertion; parietal wall covered with a thin callus. 



The type and another specimen were taken off Spondylus, at Ma- 

 zatlan, Mexico. The type has five post-nuclear whorls and measures: 

 Length 1.2 mm., diameter 0.48 mm. The type is on tablet 1985, 

 Liverpool collection, British IVIuseum. Another specimen taken 

 from Chama at Mazatlan, is on tablet 1983, Liverpool collection. 

 It is listed as Chrysallida clathratula C. B. Adams. 



IVIDELLA, new subgenus. 



=Funicularia MoNTEnosATo, Conch. Med., 1884, p. 85. Type. — Rissoa excavata 

 Philippi; not Funicularia Lamauck. + Ividia (species), Dall and Bartsch, 

 Proc. U. S. Nat. Mus., vol. 33, 1907, pp. 517-18. 



Odostomias marked with lamellar spiral ridges and equally strong 

 lamellar axial ribs, botli of which ornament spire and base. 



Type. — Odostomia (Ividia) navisa Dall and Bartsch. 



When we diagnosed Ividia"^ we unfortunately selected Parthenia 

 armata Carpenter as type. Since then we have examined Doctor 

 Carpenter's type of Parthenia armata in the British Museum and 

 find that the s];)ecies must be referred to Miralda, which necessitates 

 the selection of a new type for the group defined. Since this can 

 not be done without change of name, we propose Ividella. 



Type. — Odostomia (Ividia) navisa Dall and Bartsch. 



KEY TO THE SPECIES OF THE SUBGENIS IVIDELLA. 



Base with a single spiral lamella pcdroana, p. 172. 



Base with two spiral lamellae. 



Diameter of shell more than 1.2 mm. 



Shell robust, short navisa, p. 173. 



Shell thin, slender n. delmontensis, p. 174. 



Diameter of shell less than 1 mm orariana, p. 175. 



Base with three spiral lamellae quinquecincta, p. 174. 



ODOSTOMIA (IVIDELLA) PEDROANA, new species. 



Plate 19, figs. 8, 8a. 



Shell large, robust, chocolate-brown. Nuclear whorls two, mod- 

 erately large, forming a helicoid spire whose axis is at right angles 

 to that of the succeeding turns, in the first of which it is about one- 

 fifth immersed. Post-nuclear whorls very strongly sculptured, 



a Proc. Biol. Soc. Wash., vol. 17, 1904, p. 11. 



