192 PKOCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



simultaneously by many subgenera and genera, or an indication 

 of actual genetic relationship. Not much evidence can be adduced 

 in favour of the latter view from the recent fauna, for species of 

 widely different genera exhibit the hairs or papillae arranged in 

 obliquely decussating series ; in Hygromia, H. consona, lanuginosa, 

 etc. ... in Thysanophora, T. stigmatica and it allies ; in Eulota, 

 numerous oriental species. The list could be indefinitely increased. 

 It will be perceived from this that those authors who insist upon 

 the presence of Chloritis in tlie European Miocene fauna, stand upon 

 narrow and insecure footing." It may well be, however, that the 

 facts are somewhat intermediate between the two diverse views 

 postulated ; namely, that the character is ancient and does indicate 

 a remote common descent, but has been lost in the majority of 

 living species. It seems significant that it is specially characteristic 

 of a number of Tertiary forms. 



An examination of the anatomy of H. suhplicata shows that it 

 is not, as I had expected on account of the sculpture of the shell, 

 related to the other Helicidee of the Madeira Archipelago. It falls 

 near true Helix, of which it may be considered to represent a sub- 

 genus,- for which I propose the name Idiomela. The principal 

 characters of this monotypic subgenus (or genus ?) are as follows : — 



ImoMELA subg.n. 



Type Helix suhplicata Sowerby. Shell large, shaped essentially 

 as in H. aspersa, but apical whorls with closely set decussating rows 

 of papillee or, granules; last whorl with strong transverse plicse 

 or ribs ; periostracum brown, without bands or spots. 



Jaw strongly curved, very dense and dark, with five ribs, the 

 outer ones feeble, but the inner three strong, extending beyond the 

 margin. This is of the same general type as the jaw of H. hortensis, 

 but has fewer ribs than H. aspersa. 



Radula of the usual Helix type (Fig. la) ; the median teeth with 

 only rudimentary, non-angulate, side cusps ; laterals with similar 

 rudimentary, merely band-like, ectocones, but about the fourteenth 

 tooth a distinct cusp begins to appear, and from the eighteenth 

 onwards the main or inner cusp is bifid ; marginals trifid. The 

 radula thus differs from H. pomatia and aspersa, and resembles 

 H. nemoralis and hortensis, in the absence of salient lateral cusps on 

 the median and principal lateral teeth. The marginals are much as 

 in H. hortensis, but with very "blunt lobes on the inner part. 



Genitalia of the Helix type (Fig. 1), with large dart-sac, filiform 

 mucus glands, and very long flagellum. Dart about 9 mm. long, 

 straight, hardly constricted above the base, with four sharp longi- 

 tudinal keels at right angles to each other, the channels between 

 them with a few irregular transverse films, but they are not regular or 

 numerous, as in aspersa. Dart-sac about 11 mm. long and 4 broad, 

 the end not at all differentiated. Filiform glands not so numerous 



