346 MEXICAN BOUNDARY SHELLS— BALL. vol.xix. 



the last whorl upward thronghout the spire, but no other lamellae 

 internally. Their specimens agree with I'feiffer's types now in the 

 Dohrn collection. 



It is obvious from the preceding observations that some shells which 

 are distinctly separated by their internal features show very sinnlar 

 external characters, and I may add that the examination of large 

 numbers of s])ecimens of several species indicates that the internal 

 characters are persistent and invariable M'ithin the species. I proj^ose 

 to use these characters for arranging the genus Holosjrira into subordi- 

 nate groups as follows: 



Genus HO LOSPIRA, Von Martens. 

 TyjM'. — U. pilocerei^ Pfeiffer. 



Subgenus HOLOSPIRA, s. s. 



Axis large, with a ridge or ])lait developed in the penultimate whorl, 

 and with parietal, basal, and peripheral lamellse projecting into the 

 lumen of the whorl. 



Tiipc. — //. inlocerei, Pfeiflfer. 



This includes H. golflfussii, Menke, sp., and IT. goniostomd, Pfeiffer. 



Section BOSTRICHOCENTRTJM, Strebel and Pfeffer, 1880. 



Axis moderate, with a continuous plait on it extending from the last 

 whorl nearly to the apex. 

 Tyj>e. — H. tryoni, Pfeiffer. 

 JI. Veracruz i ana., Dall, belongs in this section. 



Section HAPIOSTEMMA, Dall. 



Eaplo8temma, Dall, Naiitilus, IX, p. 50, Sept., 1895; Proc. U. S. Nat. Mus., XYIII, 

 p. 2, 1895. 



Axis moderate, with a short, stout, axial lamella extending about half 

 a gyration in the penultimate whorl, but elsewhere simple and smooth. 

 Type. — H, meanisli, Dall. 



Section EUDISTEMMA, Dall. 



Eudintemma, Dall, Nantilns. IX, p. 50, Sept., 1895; Troc. U. S. Nat. >rns., X\III, 

 p. 3, 1895. 



Penultimate whorl with a short axial and a parietal lamella only, the 

 axis moderately large. 



Type. — 7/. arizoncnsis, Stearns. 



Section DISTOMOSPIRA, Dail. 



IHstomoHpira, Dall, Nautilus, IX, p. 50; Proc. U. S. Nat. >ru.s.. XVITI, p. 3, 1895. 



Penultimate whorl with a short strong axial and a basal hunella only ; 

 axis smooth, mrxlerately large. 

 Type. — //. bilamellatd, Dall. 



