Mr. W. H. Benson on some forms 0/ Stcnothyra. 499 



add to the information already }30ssessed respecting this curions 

 little genus. I shall begin with the typical species — 



Stenothijra Delta, Benson. 



Testa vix riinata, globoso-coiiica, lajviuscula, oblique exilissiine striata, 

 striis obsoletis spiralibus minutissimis, versus basin remotioribus, 

 decussata, jiallicle iulva, albida, vol cornea translucente ; spira co- 

 nica, acuminata, apice subtili, sutura impressa subniarginata ; an- 

 fractibus 5J, superioribus convexis, sequontibus couvexiusculis, 

 ultimo ventricoso, conipresso, \ testa; a-quaute, antice descendente, 

 supra aperturam arcuatim striato, basi compresse rotundata ; aper- 

 tura obliqua, ovato-circulari, superne indentata, peristomatis mar- 

 gine dextro acutiusculo, coluniellari ot basali expausiusculis, pa- 

 rietali intus callo inconspicuo superne truncato, niunito, extus sulco 

 impresso marginato ; operculo corueo, limbo albido. 



Long. 4-"), diam. 2|-^i^ mill. 



Hab. in locis lutosis fluvii Hooghly prope Calcutta Bengalensem, 

 satis copiose ; necnon in lacu salso prope Balliaghat, ligno natanti 

 adhaereutem ipse detexi. 



Syn. Netnatura Del fee, Bens. Journ. As. Soc. 1836, vol. v. p. 781 ; 

 Sow. Charlesw. Mag. 1837, vol. i. p. 217. 



I found it alive in both the places named ; also a dwarf variety 

 in an aqueduct, supplied by a steam-engine from the river, in 

 front of the Town Hall, at Calcutta. 



Stenothyra glabrata, A. Adams. 



Testa omnino imperforata, ovato-conica, laevissima, nitidissima, fusco- 

 coruea vel olivacea, spira couica, apice acutiusculo, sutura impressa, 

 submarginata ; anfractibus 5 couvexiusculis, ultimo ventricosiori, 

 latere sinistro sajpius gibbosulo, antice descendente, |- testae 

 sequante, basi rotundata ; apertura obliqua, rotundato-ovata, su- 

 perne angulata, peristomate recto, obtuso, plerumque nigrescente. 

 Operculo typico, concaviusculo, fusco. 



Long. Z-b\, diam. 2-3;^ mill. 



Hab. in paludibus Insulse Penang. Detexit Dr. Theo. Cantor. 



Syn. Nematura glabrata, A. Adams, Pr. Z. Soc. July 22, 1851 ; 



et var. olivacea, ejusdem, loc. cit. 

 Nematura polita, Bens. MSS., nee Sow. 



This shell, of which I have examined at least eighty speci- 

 mens, when divested of the reddish-brown earthy coating which 

 generally covers it, may be at once recognized, by its polish, 

 dark suite of colours, and freedom from sculpture and umbilical 

 rimation, independently of its form, which is more elongate than 

 the Gangetic species; also by the gibbosity of the left side of 

 the ventral volution, and the comparative absence of lateral 



32* 



