6 PEOCEEDINGS OP THE NATIONAL MUSEUM vol. 7a 



on the cone are moderately well rounded and marked by numerous 

 retractively slanting axial riblets which increase in number and de- 

 crease in strength. On the middle portion of the spire these riblets 

 become reduced and are almost obsolete. Suture well impressed. 

 Periphery of the last whorl very strongly angulated. Base short, 

 well rounded, narrowly openly umbilicated, last whorl not solute. 

 Aperture subtriangular, peristome expanded and reflected. The in- 

 ternal pillar rather stout, decidedly attenuated at the last turn. 

 There is a moderately strong fold in the penultimate whorl which 

 extends feebly into the three whorls posterior to it. 



The type (Cat. No. 363148 U.S.N.M.) was collected by C. K. 

 Orcutt in river drift near Rio Balsas Station, Guerrero, Mexico. It 

 has 12.2 whorls, and measures — length, 11.3 mm. ; diameter, 4.1 mm. 

 Cat. No. 363149 U.S.N.M. contains a paratype which is not quite 

 perfect. 



HOLOSPIRA (TRISTEMMA) HYPERIA. new species 



Plate 1, fig. 15 



Shell small, cylindro-conic, bluish white. Nuclear whorls 2.1, 

 forming a rather broad apex, well rounded, marked by fine granules 

 only. Postnuclear whorls forming a rather broad moderately long 

 apex, the apical portion well curved and marked by rather strong, 

 retractively slanting axial ribs which are a little less wide than the 

 spaces that separate them. Beyond the cone these ribs become de- 

 cidedly obsolete, reappearing only upon the last whorl where they 

 are also only poorly developed. Suture rendered conspicuous by the 

 somewhat overhanging tendency of the whorls. Periphery of the 

 last whorl well rounded. Base short, well rounded, narrowly um- 

 bilicated. Last Avhorl not solute. Aperture moderately large, sub- 

 triangular, with a decided angle at the posterior angle. Internal 

 axis moderately broad but decidedly contracted in the last turn, at 

 the posterior extremity of which the parietal fold begins and ex- 

 tends up into the penultimate whorl, disappearing upon reaching the 

 antepenultimate turn. The parietal fold and basal fold also attain 

 their maximum development in the penultimate whorl. There is no 

 indication of a labial fold. 



The type (Cat. No. 363146 U.S.N.M.) was collected by C. R. Orcutt 

 at Esperanza, Puebla, Mexico. It has 14 whorls, and measures — 

 length, 13 mm.; diameter, 4.3 mm. Cat. No. 363147 U.S.N.M. con- 

 tains two paratypes which are incomplete. 



HOLOSPIRA (HOLOSPIRA) ALVAREZENSIS. new species 



Plate 1, fig. 7 



Shell small, cylindroid, pale brown. Nuclear whorls 3.1, large, 

 forming a truncated cylindric apex. All but the last half of the 



