VARICELLA. 69 



whorls eleven, a little 'Convex, with a distinct suture: aper- 

 ture ovate, very acute above, retreating below on both sides, 

 but less on the left side : labrum thin : 'Columella moderately 

 arcuated and truncated. Mean 'divergence about 9 ; length 

 of spire .43 inch; total length .55 inch; breadth .09 inch." 

 [13.75 x 2.25 mm.]. (Adams). 



Jamaica: (Adams) ; Ipswich and Williamsfield (J. B. Hen- 

 derson). 



Achatina gracilior C. B. A., Contrib. to Conch, no. 7, p. 

 104 (April, 1850). PFR., Monogr. dii, p. 503; iv, 616; vi, 237. 



This species is related to V. costulata but differs by its more 

 slender shape, widely spaced ribs and the excessively minute 

 interstitial striation. 



No specimen agreeing fully with Adams' description has 

 been found in his collection. The single shell under the 

 name gracilior (pi. 12, fig. 8) is broken and in bad condition, 

 measuring 11.1 x 2 mm., with 9% whorls. It originally had 

 about one-ifourth of a whorl more. The first half whorl is 

 smooth, next 2% are closely obliquely striate; then follows 

 the very widely spaced rib-sculpture of .the adult stage. The 

 ribs have been worn from the later whorls, only faint vestiges 

 remaining. 



Specimens from WiUiamsfield, a place about 15 miles north 

 of Savanna-la-Mar, (pi. 12, fig. 9), and from Ipswich, in the 

 Henderson collection, seem to be referable to gracilior. One 

 from the former locality measures 8.8 x 2.1 mm., with 8 

 whorls. The ribs are nearly obsolete on the last whorl. On 

 the penult whorl there are 25 striae in the intervals. An 

 Ipswich shell has the ribs better developed, 12 or 13 on the 

 last whorl, with 36 interstitial striae. In these shells the 

 columella is moderately arcuate, and weakly truncate at base. 

 No f alse-umbili'Ciis is visible in a basal view. In an oblique 

 view, as in pi. 12 fig. 8, where the last whorl has been partly 

 broken away, the columellar margin appears nearly straight. 



The internal axis is slender and only moderately sinuous. 

 It is drawn (pi. 14, fig. 27) from a shell 8 mm. long with 

 8!/2 whorls, and having about 40 striae in the intervals on 

 the last whorl. 



