4 PROCEEDINGS OF THE NATIONAL MUSEUM vol.70 



are exceedingly poorly developed. The nucleus is flattened at the 

 summit and gives to the apex a truncated appearance. The nuclear 

 whorls plus the early postnuclear whorls increase regularly in size, 

 forming a rather long, regularly conic apex. The middle portion 

 of the postnuclear spire is almost cylindric, the whorls contracting 

 but slightly from the eleventh, which is the broadest, anteriorly. 

 The postnuclear whorls are marked by slender, well-developed, 

 slightly curved, retractively slanting axial riblets, which on the 

 conical portion of the spire are about one-third as wide as the spaces 

 that separate them. On the middle turns these riblets become much 

 more numerous, sinuous and retractively slanting. Here they are 

 about half as wide as the spaces that separate them. On the last 

 turn they again become sotoewhat strengthened, though not nearly 

 as much so as on the early turns, and also a little more distantly 

 spaced. Suture well constricted. Periphery of the last whorl ob- 

 scurely angulated. Base well rounded, narrowly openly perforated. 

 The last portion of the last whorl is solute, and here the riblets be- 

 come decidedly irregular, closely spaced and crowded, encircling the 

 entire outer surface of the turn. Aperture rather large, subquadrate 

 with the peristome reflected and expanded, particularly so basally; 

 parietal wall sinuous. 



The type (Cat. No. 363135 U.S.N.M.) was collected by C. K. 

 Orcutt at Iquala, Guerrero, Mexico. It has lT.9 whorls and meas- 

 ures — length, 25.4 mm. ; diameter, 7.3 mm. 



HOLOSPIRA (BOSTRICHOCENTRUM) EURYBIA, new species 



Plate 1, fig. 2 



Shell glnall, pupoid, bluish white, with the cone flesh colored. 

 Nuclear whorls 2.2, well rounded, all but the last half marked with 

 fine granules only. In the latter the beginnings of the axial ribs 

 of the postnuclear spire make their appearance. The postnuclear 

 turns form a broad cone which extends over the first four turns at 

 the end of which the greatest diameter is reached, and the rest of 

 the postnuclear spire begins to slowly contract. The early post- 

 nuclear whorls are moderately rounded and marked by strong, rather 

 distantly spaced curved axial riblets. The middle whorls have the 

 riblets a trifle less strong and a little more closely spaced, while on 

 the last turn the riblets become stronger and again more distantly 

 spaced. Suture well marked. Periphery of the last whorl obtusely 

 angulated. Base short, strongly curved, rimate, "marked by the con- 

 tinuations of the axial ribs. The last whorl is solute for a little dis- 

 tance, with a strong angle behind the posterior angle of the aperture 

 and a less strong one at the junction of the inner and parietal wall. 

 The solute portion is marked by ribs which are scarcely diminished 



