348 Mr. W. H. Benson on new species of Planorbis 



XXXI. — Characters of nine new or imperfectly described species 

 of Planorbis inhabiting India and China, By W. H. Ben- 

 son, Esq. 



1. Planorbis hemispha7'ula, Cantor MSS. ; Benson, Ann. Nat. 

 Hist. vol. ix. 



Testa nitida, olivaceo-cornea, leviter exilissime radiato-striata, subdia- 

 phana, supra valde convexa, spira planulata, apice vix depresso ; 

 sutura impressa ; anfractibus 4|-, ultimo extus declinato, majuscule, 

 inferne obtuse subangulato, intus laminis raris radiantibus munito, 

 subtus excavato; umbilico mediocri profundo, margine subangulato; 

 apertura obliqua subcordata, margine superiori arcuato, prominente, 

 inferiori recedente. 



Diam. major 6 mill., minor 5, axis vix 3 mill. 



Hab. in insula Chusan Imperii Sinensis. Theo. Cantor. 



In describing this shell I formerly omitted any notice of the 

 internal laminae, which indicate an approach to the more regular 

 structure observable in the English PL lineatus [segmentina of 

 Leach), as they were not very apparent through the substance of 

 the shell in the specimen examined, and are not visible in the 

 aperture. This species as well as Pl.papyraceus of the same paper 

 having been originally named by Dr. Cantor, will retain his name 

 as the authority, although the asterisks denoting that circumstance 

 have been too indiscriminately placed, as in the case of Helix ra- 

 vida, mihi, and Novaculina [Solen) constricta, Lamarck. 



2. Planorbis Calathus, nobis, n. s. 



Testa nitidiuscula, albido-cornea, vel lutescente cornea, subdiaphana, 

 exihter radiato-striata, supra convexa, versus apicem planulata, 

 apice concavo, sutura impressa ; anfractibus 4, ultimo extus de- 

 presso, inferne angulato, intus laminis denticulisque radiatis fre- 

 quentioribus munito, subtus subplanulato, versus umbilicum an- 

 gustum, profundum excavato ; apertura obliqua, cordato-sagittata, 

 intus remote labiata, margine superiori arcuato, prominente, infe- 

 riori subrecto, recedente. 



Diam. major 4f, minor 4, axis 2 mill. 



Hab. in lacubus Bhimtal et Neini Tal, regionis Kemaonensis Hima- 

 layanse ; necnon in stagnis nonnuUis agri Rohillani, prope urbem 

 Moradabad, Indiae septentrionalis. 



In a note to a paper on the singular genus Camptoceras, and 

 on the minute Melaniadous genus Tricula, contained in the 

 'Calcutta Journal of Natural History^ for 1842, I noticed the 

 unusual structure of this species, but omitted to add a specific 

 description. The shell belongs to the same type as the Chinese 

 forms above described, and with the English species PL lineatus, 

 and the Bengal PL t?'ochoides, forms a fourth species of analogous 

 but varying internal structure. 



