WEST AMERICAN PYRAMTDELLTD MOLLUSKS. 59 



Subgenus PTYCHEULIMELLA Sacco. 

 Ptycheulimclla Sacco, I. Moll, de Piemon(e e della Liguria, pi. 11, 1892, p. 59. 



Shell elongate-conic. Axial sculpture consisting of obsolete ribs 

 frequently only shown in the eaily j)ost-nuclear turns. Spiral 

 sculpture, if present, consisting of microscopic striations only. 



Type. — Tornatella pyramidata Deshayes. 



KEY TO THE SPECIES OF THE SUBGENUS PTYCHEULIMELLA. 



Shell very broadly conic ohsoleta. 



Shell slender abreojensis. 



TURBONILLA (PTYCHEULIMELLA) OBSOLETA Carpenter. 



Plate 5, fig. (i. 



? Eulimella ohsoleta Carpenter, Cat. Mazatlau Shells, 1850, p. 43(5. 



Shell broadly elongate, grayish white. Post-nuclear whorls feebly 

 rounded, marked by obsolete axial ribs which are best shown imme- 

 diately below the appressed summit. Entire surface marked by 

 extremely fine spiral lines. Aperture rhomboidal; posterior angle 

 acute; outer lip thin; columella slightly twisted and somewhat 

 revolute. 



The type which is on tablet 2011, Liverpool collection, British 

 Museum, has lost its early whorls, the four and one-half remaining 

 measure: Length 1.5 mm., diameter 0.6 mm. It comes from Mazat- 

 lan, Mexico. 



TURBONILLA (PTYCHEULIMELLA) ABREOJENSIS, new species. 



Plate 5, fig. 7. 



Shell conic, milk-white. (Nuclear whorls decollated.) Post- 

 nuclear whorls moderately well rounded, very slightly shouldered at 

 the summit, marked by mere indications of obsolete ribs near the 

 summit of the early whorls, only. Sutures well impressed. Periph- 

 ery well rounded. Base moderately long, well rounded. Surface of 

 spire and base marked by fine, closely crowded, spiral striations. 

 Aperture oval; posterior angle acute; columella rather strong, mod- 

 erately curved, somewhat revolute, provided with an oblique fold a 

 little anterior to the insertion. 



The unique type (Cat. no. 205951, U.S.N.M.) comes from Point 

 Abreojos, Lower California. It has lost the luicleus and first post- 

 nuclear whorl. The nine remaining measure: Length 5.2 mm., 

 diameter 1.6 mm. 



Subgenus PYRGOLAMPROS Sacco. 

 Pyrgolampros Sacco, I. Moll, del Piemonte e della Liguria, 1892, p. 85. 



Turbonillas with low, broad, rounded vertical ribs which almost 

 always disappear as they pass over the periphery and base of the last 



