350 MEXICAN BOUNDARY SHELLS— BALL. vol.xix. 



raised, nearly straiglit riblets with doubly wide interspaces marked by 

 somewluit irregular Hues of growth; the sculpture between the iiiuth 

 and the last whorl is more or less obsolete, but on the last whorl is 

 strong, crowded, and a little irregular; suture distinct; base a little 

 appressed; umbilical chink small; aperture as \\\ H. crossel ^hnt pro- 

 jecting l)eyond the periphery of the last whorl. Length of shell 20.."), 

 maxiniuni dianieter 5 mm. With 11. crossei, not uncommon. Ko. 



This species in form recalls H. semisciilpta, Stearns, but is smaller, 

 without the ])olished surface of the latter and of a ferruginous white 

 instead of the bluish color of H, scmisciilpfa. Tlie aperture in sonu' 

 specimens projected more than in others which seemed fully adult. 

 The internal armature consists of a short very wide flange near the 

 base on the pillar and a low but strong basal ridge extending about 

 one-third of a gyration slightly nearer the inner than the outer wall of 

 the Avhorl. 



HOLOSPIRA (HAPLOSTEMMA) MEARNSII, Ball. 

 (Plate XXXI, tig. 1.) 

 HoloHpira {llaplostcmma) mearnsii, Dall, Proc. U. S. Nat. Mus., XVIII, i>. 1, 1895. 



Shell small, compact, with 14 whorls, of which 2 are nuclear, polished, 

 and smooth; blunt above, gradually increasing to the ninth whorl and 

 subsequently slightly attenuated ; sculpture and aperture much as in II. 

 crossei, the base slightly appressed and the ribs closer and more promi- 

 nent than on the previous whorls; umbilicus not C()nsi)i('Uous; ai)er- 

 ture projecting somewhat beyond the preceding whorl, the peristome 

 hardly reflected, subtriangular, little thickened, without folds; axis 

 small, siibcylindric, with a strong, short lamella near the base in the 

 penultimate whorl. Length of shell 14.5, maximum diameter 4.5 mm. 

 Found with //. crossei, but less common. No. 129991, U.S.ISr.M. 



This species resembles H. crossei in general appearance, but is larger, 

 with more projecting aperture, and frecjuentl}' has an intercalary raised 

 line dividing the interspaces of the ribs axially. The specimens are of 

 a whitish color. 



The following species contained in the National Museum was named 

 H. tryonlj Pfeifter, on an old label, but on comparison with the litera- 

 ture proved to be quite distinct from that species, which is asserted by 

 Crosse and Fischer to be quite destitute of internal armature. 



HOLOSPIRA (BOSTRICHOCENTRUM) VERACRUZIANA, Dall. 



Holospira {liostrichocentriim) veravruziana, Dall, Proc U. S. Nat. Miis., XVIII, 

 p. 4, 1895. 



Shell closely resembling the enlarged figure of //. microstoma, 

 Pfeiffer,^ but with a shorter apical cone and larger aperture. According 



* 1 Crosse and Fischer, Miss. Sci. au Mexique, Moll., p. 337, pi. xvii, figs. 9, 9a. 



