178 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXV. 



suture a channeled look; axial sculpture of numerous (on the penul- 

 timate whorl about 80) slightly elevated threads, equal and more or 

 less equally distributed, rising abruptly from the surface of the 

 whorl with the much wider interspaces flattish between them; the 

 threads are concavely arcuate and slightly retractive; on the base 

 they are continued to the axis, closer and sometimes bifurcate; the 

 same sculpture as that on the permanent whorls also appears on the 

 truncate portion of the spire; aperture produced, with a slightly 

 reflected entire lip; form of the opening obscurely triangular; axis 

 proportioned as figured, the ribs of the fringe in the penultimate 

 whorl showing a tendency to break up into drops or beads; in the 

 upper part of the spire, as the axis becomes attenuated, the ribs are 

 less prominent, less distinct, and less numerous; on the later whorls 

 they number about 2 to a millimeter; there are about 28 in the last 

 whorl containing them; they are slightly retractively oblique and 

 tend to overlap each other in a forward direction. The measure- 

 ments of several adult specimens are as follows, in millimeters: 



Type.— Cat. No. 198083, U.S.N.M. Collected at Tamaulipas, 

 Mexico, by Dr. Edward Palmer. 



There is some variation in the outlines of the shells, some being 

 more cylindrical, and in others the maximum diameter is not always 

 in the same relative position. 



Genus STREPTOSTYLA Shuttleworth. 



STREPTOSTYLA BARTSCHII Dall, new species. 



Plate XXIX. fig. 1. 



Shell short, stout, subcylindric, with 71 whorls, a thin yellow- 

 brown periostracum over a milk-white test; spire bee-hive shaped, 

 bluntly pointed, with moderately convex whorls; first 2^ whorls 

 smooth, polished, white: subsequent whorls by degrees more strongly 

 sculptured with fine, nearly vertical, close-set, rounded, slightly 

 flexuous riblets, subequal and subequally distributed, with very nar- 

 row interspaces, and extending from suture to suture; on the last 

 whorl the riblets are decidedly feebler in front of the middle of the 

 whorl; suture deep, distinct, not channeled or appressed; aperture 



