Mr. W. H. Benson on new forms of Cyclostomacea. 227 



the crenulation or denticulation along the callous interior of the 

 right lip. The teeth are twelve in number, and are disposed in 

 pairs. The incision resembles that observable in some of the 

 species of Pterocyclos, and there is a slight disposition towards 

 the formation of a wing. 



5. Alycaus armillatus, n. s. 



Testa umbilicata, depresso-turbinata, costulata ; spira conoidea, su- 

 tura impressa, apice obtuse ; anfractibus 3^ convexis, ultimo ad 

 latus inflato, confertius costulato, tum constricto, antice tumido, 

 Iseviori, tubulo suturali brevi, ab apertura remote, munite ; aper- 

 tura obliqua eirculari, peristemate duplici, interne valde perrecto, 

 continue, margine simplici, extus striate, exterieri expanse, re- 

 flexiuscule ; umbilice subaperte. Opercule ? 



Diam. major 2, minor l|, axis \^ mill. 



Hab. ad Thyet-Mio cum prsecedente. 



The exterior expanded peristome, forming a conspicuous collar 

 round the porrect interior portion, is the most prominent cha- 

 racter in this very minute species. The only specimen received 

 is in a weathered condition, and so much bleached that the 

 colour of the perfect shell cannot be ascertained. 



Five new forms have here been added to this curious restricted 

 genus, which now contains nine species, three of which are 

 Himalayan, one Cochin-Chinese, and one [A. Spiracellum, A. & 

 R.) from Borneo. The Ultra- Gangetic region must at present be 

 considered the head- quarters of the type. 



6. Pterocyclos pullatus, n. s. 



Testa aperte umbilicata, convexe-depressa, confertim radiato-stri- 

 atula, nigrescente-castanea, superne strigis lutee-albidis, fulguratis, 

 fasciaque saturata ornata ; spira cenvexa, sutura profunda, apice 

 preminule; anfractibus A\ convexis, ultimo longe descendente, 

 subtus cenvexe ; apertura vix obliqua, eirculari ; peristomate du- 

 plici, interiori breviter perrecto, superne sinu mediecri latiuscule, 

 interrupto, exterieri vix expansiuscule, superne alam subrevelutam 

 semicucullatam, antice breviter descendentem obtusam, ab anfractu 

 penultimo distantem effermante ; umbilice mediecri, prefundo, 

 perspective. Opercule intus concave, extus cencaviuscule, scabre ; 

 anfractuum marginibus elevatis ; margine laterali lato, lamellis 

 acutis spiralibus munite. 



Diam. major 13, minor \\\, axis 6 mill. 



Hab. ad Akaeuktong, prepe fluvium Irawadi, satis frequens. 



The less depth of the interior hollow of the operculum and 

 the structure of the wing show a departure from the typical 

 species of Pterocyclos^ which becomes more apparent in the 

 southern form next to be described. 



15* 



