Mr. W. H. Bcnsou on Clostopliis crwcf Rhiostoina. 97 



genus Aulopoma ; but the acquisition of an operculum induced 

 liiui to class it with Pterocyclos, as Pfeiffer has in fact done with 

 two allied species from Siam and Cochin China, although he 

 has referred the former, Cycl. Housei, Haines, to the second 

 section of Pterocyclos, " anfractu ultimo spiraculo munito," in 

 company with Pt. hispidus, Pearson, in which the construction 

 and site of the spiracle are very different; while he has placed 

 the Cochin Chinese species, Pt. tenei', Menke, in his third sec- 

 tion. It is evident that the solute apertm-e, coupled with the 

 incision at the top of the aperture and the subtubular promi- 

 nence crowning the slit in both these species, separate them 

 from all known Pterocycli, and associate them with the Burmese 

 species now described. 



Another feature common to the Tenasserim and Siamese 

 Rhiostomata exists in the keel extending from the tubular pro- 

 cess to the suture at the junction of the penultimate whorl, and 

 not noticed in R. tener. 



Sp. 2. Rhiostoma Housei, Haines. 



Syn. Pterocyclos, Pfr. No. 3. sect. 2. Mon. Pneum. Su])pl. 

 Cyclostoma, Haines, Ann. Lyceum, New York. 



Hub. Siam. 



Sp. 3. Rhiostoma tener, Menke. 



Syn. Pterocyclos, Menke, Mai. Blatter, 1856. 



Pterocyclos, Pfeiffer, No. 15. sect. 3. Mon. Pneum. Suppl. 



Hab. Turon, Cochin China. 



The long- lost Turbo foliaceus, Ch., which, on the authority of 

 Dillwyn, has been unaccountably confounded with the very 

 distinct Socotrine species, Otopoma naticoides, Kecluz, proves 

 to be an inhabitant of the Andaman Islands. A small variety, 

 forwarded by ]Mr. Theobald, may be at once recognized as that 

 species by its form, colour, and distant variciform plicse on the 

 last whorl behind the aperture. Were it not for a thin Cyclo- 

 phoroid horny operculum, stated to belong to this siiell, I should 

 have been disposed to place it in Otopoma. The plicae vary in 

 number, and are even altogether wanting. 



A small Helix, a Streptaxis, and a Helicina accompanied 

 C. foliaceus, and were collected in the same locality, unexplored 

 since the date of Dr. Heifer's fatal attempt. 



Cheltenbam, Januarv 5, 1860. 



