DESCRIPTIONS AND FIGURES OF SOME LAND AND 

 FRESH- WATER SHELLS FROM MEXICO, BELIEVED TO 

 BE NEW. 



By William Healey Dall, 

 Curator, Division of Mollusks, U. 8. National Museum. 



In 1907 Dr. E. Palmer sent in to the United States National Mu- 

 seum a few land shells from Tamaulipas, Mexico, two of which 

 appear to be undescribed, one of them exhibiting a new form of arma- 

 ture on the axis. These are here described, and to these are added 

 some species collected by Nelson and Goldman in 1898, which, though 

 recognized as new and figured at that time, have not hitherto been 

 published. 



Genus CCELOCENTRUM Crosse and Fischer. 



Section CROSSOSTEPHANUS Dall, new. 



A Cceloeetttnint with axis armed with a turgid spiral ridge, extend- 

 ing through the space of several whorls and axially sculptured with 

 numerous cord-like short ribs, which on the anterior face of the 

 ridge overhang like a fringe, ceasing with the penultimate whorl : the 

 axis in the last whorl behind the last half of the whorl is twisted 

 and obliquely truncate. 



Type- — Co'locentnon pal uteri Dall and Bartsch. 



CO2L0CENTRUM (CROSSOSTEPHANUS) PALMERI Dall and Bartsch, new species. 



Plate xxix. figs. •_'. 5. 



Shell with more than twenty-four whorls of which, in the adult, 

 about thirteen remain, the rest having been detached: color a 

 bright yellowish brown when fresh, the interior of the aperture 

 whitish: whorls moderately rounded, obsoletely spirally striated: 

 sculpture consisting of a thread-like hue keel just in front of the 

 suture, which is flattened behind it ; a second wider and less distinct 

 thread marginates the base; the effect of these threads is to give the 



Proceedings U. S. National Museum, Vol. XXXV— No. 1642. 

 Proc. X. M. vol. xxxv — 08 12 177 



