OF CONCHOLOGY. 



II. 



307 



Two species of small heliciform land-shells, of which I gave 

 descriptions in the Annals and Magazine of Natural History 

 (4 ser. i, p. 440), under the names respectively of Zonites impli- 

 cans, and Z. umbrafilis, require pictorial illustration to render 

 clearer their differences. I take the opportunity of appending 

 sketches of them.* Plate 17, figs. 2 and 3. 



Two other species present some resemblance to the Helix 

 harpa of Say, and probably may be found to belong to the same 

 group [Zougenetes of Morse). These I have described in the 

 Proceedings of the Scientific Association of Trinidad (Dec, 

 1868), as Helix ierensis and H c<xca. Of the former, I append 

 a sketch. PI. 17, fig. 4. H. cceca difiers in being more elevated 

 and less openly umbilicated, and in having a nearly circular 

 rather than a lunate aperture. Mr. Ralph Tate has found H. 

 ierensis in Venezuelan Guiana and St. Lucia, and in Nicaragua 

 he has discovered an allied form {H. ccecoides, Tate). 



Helix bactricol/i, a species described by me in the Annals of 

 Natural History (1. c), is of a very different type. The sketch 

 (pi. 17, fig. 5), does not exhibit very clearly the character of the 

 costellation, but it will serve to give an idea of the shape of the 

 shell. The ornamentation is of the same character as that of 

 H. rotundata, MUU., and H. perspectiva, Say, and the sliaj^e of 

 the whorls and umbilicus is also similar. H. hactricola is much 

 more elevated ; but that character, although it might be scarcely 

 in accordance with the existing technical definition of the group 

 Patula (depressa, discoidea, vel turbinata), ought not, in my 

 opinion, to exclude the Trinidad species from it. 



III. 



I have recently been fortunate enough to discover additional 

 examples of Bidirnulus aiireolus. Tlie specimens from which 

 the species was described by me in the Annals and Magazine of 

 Natural History (1866) were young and imperfect. The adult 

 shell has 6| — 7 whorls; its lip is acute and slightly effuse. It 

 is generally of the most beautiful transparent yellow, but I have 

 found some white examples, and a banded variety is not uncom- 

 mon. The latter bears considerable resemblance to B. midti- 



* There was an error in my original description of Z. umhratilis. The 

 umbilicus is not wider than in Z. implicans, but it is deeper. The figures 

 here given are of extreme forms. 



