32 On some Helices //-om West Australia and the Mauritius. 



depresso-conoidea, apice obtuso, sutura impressa ; anfractibus G^- 

 angiistis, ultimo rotundato ; apertura lunata, vix obliqua ; peristo- 

 mate acuto, margine columellari calloso, albido, obliquo, abrupte 

 truncate, dentem efformante. 



Diam. major 17, minor 15, axis 9 mill. 



Syn. Helix Monodonta, Grat., nee Lea. 



Hab. ad Moka, Insulae Mauritii, rarissime. Teste Sir D. W. Barclay. 



The structure of the tooth is more conspicuous in the young 

 shell, before the columella has become thickened by the callous 

 enamel, and it appears to be caused by the abrupt termination 

 of a winding plait on the columella. 



I am indebted to Dr. Traill for specimens of the Bornean spe- 

 cies of Cyclostoma described in pp. 269-270 of the 10th volume 

 of the ' Annals,^ and for information regarding the localities of 

 those and some other species collected by himself. 



C. Anostoma, nobis, was found by him in the depths of the 



forest on the island of Labuan, invariably on the leaves of trees. 



C 4-Jilos>j,m, nobis. Pulo Pappan, near Labuan, among dead 



leaves, on clayey ground. It is difficult of detection from being 



always covered with a coating of clay. 



C. vitreum, Lesson. This widely spread species, which is met 

 with from the Straits of Malacca to the islets on the N.E. coast 

 of Australia, is met with in Pulo Pappan, as in the Frankland 

 Isles, on leaves of trees. 



C. sericatum, Pfr. Pulo Daat, near Labuan, on leaves of trees. 

 Ptei'ocyclos biciliatufi, Mousson {Cycl. Charhonnieri, Kecluz, 

 Jour, Conch. 18.51). Sarawak, Borneo, brought by the Dyaks, 

 and containing generally eight or ten eggs. 



Mr. Metcalfe had already announced (Zool. Proc. 1851) that 

 Pt. biciliatus of Mousson was a native of Borneo, and not of 

 Burmah, as supposed by Mousson. It is clear, from Reclnz's 

 figure and detailed description, that it is the same as CycL [Pte- 

 rocyclos) Charbonmeri, brought by Dr. Charbonnier from Borneo. 

 The faint indentation noticed by Mr. Metcalfe at the upper part 

 of the aperture is shown, in perfect specimens, to represent the 

 true wing of Pterocyclos ; and underneath is the obsolete sinus, 

 corresponding to that observable in Pt. hispidus, Pearson {spira- 

 culu/n, Sow.), which is also provided with a similar retroverted 

 tube in the suture, behind the aperture. Recluz notices this 

 structure of the peristome, but erroneously considei-ed it to be 

 the indication of a second, but imperfect canal. Pt. hispidus and 

 Pt. biciliatus have another feature in common in a hispid epi- 

 dermis ; but in the smaller species this is developed into long 

 bristles on the double keel. They both deviate from the true 

 type of Pterocyclos, especially Pt. biciliatus, in which, as remarked 



