PLANORBIS, 1^5 



252. Planorbis (Segmentina) umbilicalis {Benson). 



PUmorbis {.'SeymeiUbia) umbilicalis (i;eiison), .). A. S. 1'.. v. 1^3(5, 

 p. 741; A.'M. N. H. ser. 2, v, 1853, p. 3.51; Martens. Mai. 

 Bliitt. xiv, p. 21(i; 11. .t T., C. T. pi. 40, figs. 7-9; Sowerby 

 in lleeve, Conch. Icon, xx, pi. 10, fi--. 77 ; Clessin, in Conch.- 

 Cak 1884, p. 1.36, pi. lo, %. (i. 



OrirjinaJ description : — Testa quasi dextra luteo-cornea, polita, 

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

 versus umbilicum jjrofundum spectantibus, ultimo interiores pene 

 tegente; supra convexa versus apicem planata, apice concavo, 

 omnibus aiifractibus satis apparentibus ; peripbajria obtuse 

 anc;ulata. 



The dimensions as given by Clessin are as follow : — 



Alt. 2, diam. S-.o mm. 



Hah. Sylbet. 



2.53. Planorbis (Segmentina) trochoideus (Benson). 



rianorhis (Setpnentiiia) troc/ioidey.i (Bensnu), J. A. S. B. v, 1836, 

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

 ser. 2, v, 1850, p. 3.-)2 ; II. & T., C. 1. pi. 39, figs. 4-6; 

 Sowerby in Eeeve. Conch. Icon, xx, pi. 9, fig. 70 ; Clessin, m 

 Conch.-Oab. 1885, p. 22.1 



Oriyinal description -.—Testa (juasi dextra diaphaua, subtro- 

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

 quasi umbilicali ; anfractibus omnibus parum apparentibus, sutura 

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

 contracto. Aufractu ultimo majori reliquos amplectente, supra 

 pene, infra omnino obtegcnte ; peripbgeria acuta. 



Alt. scarcely 2, diam. 3 mm. 



Hcth. Barrackpore. 



254. Planorbis (Segmentina) gruneri (Clessin). 



Planorbis {^Seqmentina) (/rancri (Clessin), in Conch. -Cab. 1884, 

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



Original descrijdion -.—Testii depressa, supra centro paululum 

 concavo, snbtus subplanata, nitidula subtilissime irregulariter 

 striata, diaphaua. cornea ; anfr. 4.4 lente et regulariter accrescente.s, 

 depresso-ovati, utrinque convexiusculi ac sutura profunda separati; 

 ultimus penultimo vix duplo latior ; apertura obliqua, ovata; 

 peristoma aciitum, marginibus disjunctis ; margine superiore 

 paululum producto. 



Alt. 8, diam. 5 mm. 



ITcdK India; Singapore. 



