PLANORBIS. 125 



252. Planorbis (Segmentina) umbilicalis (Benson). 



Planorbis (Seymentina) umbilicalis (Benson), J. A. S. B. v, 1836, 

 p. 741 ; A. M. N. H. ser. 2, v, 1853, p. 351 ; Martens, Mai. 

 Blatt. xiv, p. 216; H. & T., C. I. pi. 40, figs. 7-9; Sowerby 

 in Reeve, Conch. Icon, xx, pi. 10, fig. 77 ; Clessiu, in Conch.- 

 Cab. 1884, p. 136, pi. 15, tig. 6. 



Original description : Testa quasi dextra luteo-cornea, polita, 

 leviter radiato-striata, infra excavato-depressa, anfractibus omnibus 

 versus umbilicum prol'undum spectantibus, ultimo interiores pene 

 tegeute; supra convexa versus apicem planata, apice concavo, 

 omnibus anfractibus satis apparentibus ; periphaaria obtuse 

 angulata. 



The dimensions as given by Clessin are as follow : 



Alt. 2, diam. 8*5 mm. 



Hab. Sylhet. 



253. Planorbis (Segmentina) trochoideus (Benson). 



Planorbis (Segmentina) trochoideus (Benson), J. A. S. B. v, 1836, 

 p. 742 (Glean. Scien. Calcutta, i, pi. 8, tig. 10) ; A. M. N. H. 

 ser. 2, v, 1850, p. 352; H. & T., C. I. pi. 39, tigs. 4-6; 

 Sowerbv in Reeve, Conch. Icon, xx, pi. 9, fig. 70 ; Clessin, in 

 Conch .-Gab. 1885, p. 225. 



Original description : Testa quasi dextra diapbaua, subtro- 

 chiforini, supra glabra, rotundato-convexa, apice concavo-depresso 

 quasi umbilicali ; anfractibus omnibus parum apparentibus, sutura 

 excuvata divisis ; infra radiatim striata, truncata, planata, umbilico 

 contracto. Anfractu ultimo majori reliquos ainplectente, supra 

 pene, infra omnino obtegcnte ; peripbaeria acuta. 



Alt. scarcely 2, diam. 3 mm. 



Hob. Barrackpore. 



254. Planorbis (Segmentina) gruneri (Clessin). 



Planorbis (Segmentina) gruneri (Clessin), in Conch. -Cab. 1884, 

 p. 148, pi. 21, tig. 9. 



Original description : Testa depressa, supra centre paululum 

 concavo, subtus subplauata, nitidula subtilissime irregulariter 

 striata, diaphana. cornea ; anfr. 4| lenteet regulariteraccrescentes, 

 depresso-ovati, utrinque convexiusculi ac sutura profundaseparati; 

 ultinius penultimo vix duplo latior ; apertura obliqua, ovata ; 

 peristoma acutnm, marginibus disjunctis ; margiue superiore 

 paululum producto. 



Alt. 8, diam. 5 mm. 



Hob. India ; Singapore. 



