70 EOCENE MOLLUSCA. 
they are not continued towards, and do not appear at, the aperture. The columellar 
lip does not present any evidence of teeth. The umbilicus is rather small. 
On comparing this shell with 7. /abyrinthica, the distinctions appear to be that, in 
the present species, the apex is more obtuse, approaching, in that character, more nearly 
to the recent specimens of that species; the whorls enlarge more slowly, are more 
roundedly convex, and but slightly, if at all, flattened on the base; the aperture, 
partaking of the character of the whorls, is rounder, and the teeth, if present, are on 
the outer lip, and not on the columellar lip, as in H. dabyrinthica ; the umbilicus is 
smaller, and, if the shell were preserved, would, I think, be nearly closed. 
Having only seen the single specimen in my collection, I propose the species with 
hesitation, although the characters seem to me sufficient for specific distinction. 
Size.—Hlevation 1-10th in. nearly; diameter 1-10th in., nearly. 
Locality—Headon Hill. 
No. 22. Hetrx Heaponensis. Ff. /. Hdwards. Tab. XI, fig. 5 a—d. 
H. testd minutd, orbiculari, sub-depressd, umbilicatd ; spird prominuld ; anfractibus sex, 
rotundatis, suturis perspicuis : apertura rotundato-semi-lunari, obliqud ; peristomate tncras- 
sato, refleco ; margine externo tribus lamellis, penitissime decurrentibus, instructo : umbilico 
lato, profundo. 
A very small depressedly orbicular shell, with a somewhat elevated spire, com- 
posed of six or seven rounded whorls, separated by a deep suture; the rounded 
aperture is oblique, and impinged upon by the body whorl, which gives to it a semi- 
lunar shape; the peristome is slightly thickened internally, and reflected ; and the outer 
lip is furnished with three lamelliform teeth, extending far back into the whorls; the 
umbilicus is wide and deep. 
The H. Headonensis is apparently extremely rare; my specimen, which I believe to 
be unique, is merely a cast, and the outward condition of the shell is not shown. The 
species presents some analogy with the depressed variety of 1. /abyrinthica; but the 
greater number of the whorls, and the different dentition of the aperture, distinguish it 
from that shell. In general appearance it resembles the recent H. pulchella ; but the 
spire is more elevated, the whorls more numerous, and, in the latter species, the 
aperture is without the plaits which characterise the present shell. The species 
appears to be well marked and perfectly distinct. 
Size.-—KHlevation rather more than 1-20th in.; diameter 1-10th in. 
Locality—Headon Hill. 
