348 MEXICAN BOUNDARY SHELLS— BALL. vol.xix. 



radnla, the latter with a transverse series of 36: 1 :3r>. For this division 

 oftlie genus Mr. Pilsbry jjroposed the sectional name Olu/ostylKs, of whieh 

 Eucalodluni hJandlanum, Crosse and Fischer, serves as the type. The 

 relation of these two groups to each other recalls that of Bo,stHchocen- 

 trum to Mctastoma among the TTolospiras. In the genus Cerion I have 

 already divided the group into sections characterized by the internal 

 lamina^, whi(;h appear to a fiord good characters and recall to some 

 extent the features exhibited internally in Hoh,spira. There is a curi- 

 ous similarity in general form and top heaviness between many of the 

 species of Cerion and IloJoapira. 



In this connection I have added the descriptions of four Mexican 

 species belonging to Coeloccntrum, Anisospira and Strepfostyla, which 

 were obtained l»y Mr. E. W, Nelson while exploring for the United 

 States Department of Agriculture in this region, as it seemed desirable 

 to concentrate the published data on this fauna and would add to the 

 interest of this report. 



HOLOSPIRA (METASTOMA) CROSSEI, Dall. 

 (Plate XXXI, fig. 2.) 

 Holospira {Metasloma) crossei, Dall, Proc. U. S. Nat. Mus., XVIII, p. 3, 1895. 



Shell small, comi^act, 12-wliorled, of a brownish gray color; nuclear 

 whorls 2, smooth, polished, apically blunt, succeeding 4 gradually and 

 evenly increasing, after which the shell is cylindrical; sculpture of 

 pretty even, slightly oblique, rounded riblets, extending from suture to 

 suture and separated by interspaces twice as wide as the ribs; suture 

 distinct; base rounded, with a shallow umbilical chink; aperture sim- 

 ple, slightly oblique, not projecting beyond the periphery of the pre- 

 ceding whorl, the lip slightly exi)anded in front of a faint constriction, 

 the opening subcircular without internal ridges, the outer anterior part 

 obtusely angular; axis small, regularly increasing to the last whorl, 

 not inflated. Length of shell 11, maximum diameter 4 mm. 



Top of Hachita Grande Mountain, Grant County, New Mexico, Dr. 

 Mearns. No. 129989, LT.S.N.M. 



This species resembles H. f/ohlfussH, Menke, but is slightly smaller, 

 with a shorter neck to the aperture and a less reflected and triangular 

 peristome. It is entirely destitute of the remarkable internal lamelhe 

 which characterize Jf. f/old/nssii. It is named in honor of M. II. 

 Crosse, who has numographed the genus. 



HOLOSPIRA (METASTOMA) PASONIS, Dall. 

 (Plate XXXI, li<;-8.4,5.) 

 Holospira pasonis, Dall, Tlie Nautilus, VIII, p. 112, Fel)., 1895. 



This fine species was obtained by Mr. Singley fiom a collection made 

 at Mule Canyon, Kl Paso County, Texas, at an elevation of 4.000 feet. 

 As it belongs to the same general region and may be advantageously 



