MONOGRAPH OF BRITISH LAND AND FRESHWATER MOLLUSCA. 201 
Genus THELIDOMUS Swainson. 
Thelidomus occlusus (Edwards). 
Helix occlusa Edwards, Mon. Eoe. Moll., 1852, p. 64, pl. 10, ff. 10 a-e. 
Nanina ocelusa Sandb., Vorwelt, 1872, pp. 228 and 294, and pls. 13, ff. 15-15b, 
Hil Wiis wits PANT 
Ariophanta (Rhysota) ocelusa Cossmann, Coq. Foss. Eoe. Paris, 1889, p. 352. 
SHELL subglobular, more convex above than below ; WHORLS five to six, con- 
vex, rapidly enlarging, depressed at the sutures and flattened at the base, the lines 
of growth faint, oblique and irregular; APERTURE obliquely oval, the ends 
slightly converging, and the Lip slightly reflected, but basally spread over and 
entirely closing the narrow UMBILICUS ; a brownish-yellow peripheral band encircles 
the whorls just above the sutural line, the colouring being always preserved. 
Diam. 30 mill. ; alt. 19 mill. 
iets 
WSO 
Thelidomus ocelusus (Edwards). 
Fic. 254.—Frontal and rear aspect of specimens with shell preserved, and showing the 
peripheral banding (after Edwards). 
a 
s 
Thelidomus occlusus (Edwards). 
Fic. 255.—The rear, basal, and frontal aspects of casts (after Edwards). 
Mr. Edwards remarks that the species is readily distinguishable when 
the shell is preserved, but that casts are more commonly found, and these 
resemble the casts of young H/. globosa, but may be separated by the 
oblique columella and flattened base, so different from the tumid base 
and almost vertical columella of globosa, while the smaller number of 
whorls and narrower umbilicus separate it as clearly from //. vectiensis 
and H. d@urbani. 
Mr. Gardner remarks on the strong resemblance of this species to 
FA. incerta Fér., a native of St. Vincent and the West Indies, while Prof. 
Sandberger is struck by the similarity not only in form, but in general 
aspect and banding to Manina moussoni, and Cossmann has directed 
attention to the similarity of the fawn-coloured peripheral band to that 
of Ariophanta monozonalis of Lamarck. 
Upper Eocene—In Germany, according to Prof. Sandberger, it is not searce at 
Buxweiler, Alsace. 
In France, M. Cossmann records it from the middle sands and limestones of St. 
Ouen ; and fragments of shell from Le Fayel and Berville. 
Oligocene—In the Isle of Wight, it is, according to Edwards, not rare at Sconce, 
in the lower beds of the Bembridge limestone, in which series Mr. Charles Ashford 
gives Bembridge, Hempstead, Whitecliff Bay, ete., as additional localities. 
Mr. Gardner regarded all the Bembridge limestone specimens as young H. globosa, 
and limited 7. ocelusa to the Headon series; although Mr. Edwards in the corri- 
genda of his work eliminated the Headon record as incorrect. 
