Mr. AV. II. Benson on new forms 0/ Cyclostomacoa. 2'Z7 



the crenulation or dentieulation 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-turbiuata, costulata ; spira conoidea, su- 

 tura impressa, apice obtuso ; anfractibus 3\ convexis, ultimo ad 

 latus inflate, confertius costulato, turn constricto, antice turnido, 

 Iseviori, tubulo suturali brevi, ab apertura reuioto, munito ; aper- 

 tura obliqua circulari, peristomate duplici, interno valde porrecto, 

 continuo, margine siniplici, extus striato, exteriori expanse, re- 

 flexiusculo ; uiiibilico subaperto. Opercule ? 



Diam. major 2, miner 1|, axis 1^ mill. 



Hab. ad Thyet-Mie cum prsecedentc. 



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. & 

 11.) 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, cenvexo-depressa, cenfertim radiato-stri- 

 atula, nigrescente-castauea, superue strigis Uiteo-albidis, fulguratis, 

 fasciaque saturata ornata ; spira convexa, sutura profunda, apice 

 prominulo ; anfractibus 4^ convexis, ultimo longe descendente, 

 subtus convexo ; apertura vix obliqua, circulari ; peristomate du- 

 plici, interieri breviter porrecto, superne sinu mediocri latiuscule, 

 interrupto, exteriori vix expansiusculo, superne alam subrevolutam 

 semicucullatam, antice breviter descendentem ebtusam, abanfractu 

 penultimo distautem efformante ; umbilice mediocri, prefunde, 

 perspective. Opercule intus concave, extus cencaviuscule, scabro ; 

 anfractuum marginibus elevatis ; margine laterali late, lamellis 

 acutis spiralibus munito. 



Diam. major 13, minor Hi-, axis 6 mill. 



Hab. ad Akaouktong, prope 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* 



