COELOCENTRUM, SUBG. SPARTOCENTRUM. 51 



Subgenus SPARTOCENTRUM Dall, 1895. 



Spartocentrum DALL, Nautilus ix, p. 51, type C. irregulars 

 Gabb. Tcn<ri/i<t J. MABILLE, Bulletin cle la Soc. Philoma- 

 thique de Paris (8), ix, 1896-1897, p. 79, types Berendtia 

 <]i<jucti and B. niinoritta ]\Iab. 



Shell, mauy-whorled, slender, cylindric below, tapering 

 above, retaining the apex entire. Apex bulbous, the first 2,y 2 

 whorls vertically costellate, following 2 whorls decussated, 

 granose, subsequent whorls ribbed, the last with no trace of a 

 subperipheral cord, adnate or becoming free. Internal axis 

 hollow, smooth, somewhat sinuous within each whorl, having a 

 spiral swelling or convexity. Type C. irregulars. 



The species of this group are all from the arid plateau of 

 the central portion of Lower California. They differ from 

 the geographically separated Mexican group in retaining the 

 early whorls in adult life, in the special sculpture of these 

 whorls, and in the attenuation of the shell, which approaches 

 Epirobia in form. Berendtia has similar apical sculpture, but 

 differs in the very slender and imperforate axis. 



Key to Species. 



I. Last whorl in contact with the preceding one to the aper- 

 ture, the upper margin of the peristome adnate. 



irregulars, p. 51. 

 II. Last whorl becoming free in front. 



1. No interstitial striae between the riblets. 



a. Whorls 21-22 in a length of 23.5 mm. ; diam. 2.7 

 mm. ; riblets on penult, whorl about 47. 



eisenianum, p. 55. 



6. Whorls 161/0-181/2 in a length of 24-25 mm.; 

 diam. 4.5 mm. ; riblets about 62 on penult, whorl. 



minorinum v. gabbi, p. 54. 



2. Striae in the intervals between riblets ; whorls 19-20 ; 

 length 301/2-33 ; diam. 5 mm. digueti, p. 56. 



C. IRREGULARE (Gabb). PI. 13, figs. 15, 16 ; pi. 17, fig. 24. 



Shell rimate, narrowly umbilicate or perforate, cylindric- 

 tapering, thin; white or pale reddish-brown in the bleached 



