56 COELOCENTRUM, SUBG. SPARTOCENTRUM. 



Umbilicus small. Sculpture: first 2% whorls bearing very 

 close, fine, delicate vertical riblets; next 2 whorls with these 

 riblets cut into granules by spiral decussating lines ; following 

 whorls with close, fine, slightly arcuate riblets, about 47 in 

 number on the next to last whorl. Aperture decidedly ob- 

 lique, rhombic, its length contained nearly eight times in that 

 of the shell; peristome thin, continuous, slightly expanded 

 throughout. Internal axis smooth, sinuous, strongly swollen 

 near the base within each whorl. 



Alt. 23.5, diam. of last whorl above aperture 2.7, length of 

 aperture 3 mm. ; diam. of second whorl of the apex 1.3 mm. 



Lower California (Fred. L. Button). 



C. eisenianum PILS V .Proc. Acad. Nat. Sci. Phila., 1900, p. 

 553 (Nov. 10, 1900). 



This species differs from C. minorinum var. gabbi in the 

 following respects : With the same length it has a much more 

 slender form, more numerous and narrower whorls, coarser 

 eostulation and a smaller aperture. The apical whorls are, 

 moreover, rather more club-shaped. It is not closely related 

 to any other species known. 



In one specimen (pi. 17, fig. 25) the last whorl is more ex- 

 tensively free in front, and descends much more. 



C. DIGUETI (Mabille). 



Shell subrimate-perforate, cylindric, tapering towards the 

 apex, somewhat thin and rather fragile, a little opaque, desti- 

 tute of cuticle, grayish-buff, scarcely shining; beautifully 

 ornamented with obtuse, lamellose riblets, their interstices 

 seen under a lens to be quite regularly set with very minute 

 arcuate striae and riblets. Apex obtuse, mammillate; 4 to 5 

 embryonic whorls cancellated and beautifully granulose. 

 Whorls 19-20, convex, slowly and regularly increasing, the 

 last equal to the penultimate and slightly exceeding the ante- 

 penultimate in width; separated by a deep suture; the last 

 whorl free, rounded, slightly tapering, descending in front, 

 carinated at its insertion, with a short, obtuse keel surround- 

 ing the umbilical perforation. Aperture oval, angulate above, 

 obscurely channelled below at the base of the columella. 



