56 COELOCENTRUM, SUBG. SPARTOCENTRUM. 



Umbilicus small. Sculpture: first 2 1/2 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., 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 

 costulation 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. 



