79 



hcring to tlic last wliorl. Coluinclla tlilnly callous. Oper- 

 culum horny. 



Assiminca was first discovered in tlic Bay of Naples and 

 afterwards in Britain. Ssveral allied forms occur in India and 

 China. There is a globose form in Chili, and the genus 

 appears to be represented by Amnicola in N. America. But as 

 the determination of the genus rests more upon the structure 

 of the animal than the shell, and as the new European species 

 have not been examined, the identification must remain 

 doubtful. For the information of observers who may pursue 

 the subject, the following is the description of the animal. 

 Body small ; head produced into a ringed muzzle notched in 

 front, tentacles short, united with the eye pedicels and hearing the 

 eye at the summit, foot ample, broad in front, short and rather 

 obtuse behind, carrying a slight horny, few whorled oper- 

 culum. 



1. AssiMiNEATASMANiCAW.s. Atestaturhinato-conica,parva, opaca, 

 pallUle viridi, intus fiilva ; cpidcrmide olivacea (sapi corrosa) ; spira 

 acuta ; anfractibus (5) planatis, apcrhira fidva. 



Shell turbinately conical, small, opaque, pale green, fulvous 

 within with an olive epidermis (often corroded), spire acute, 

 whorls (5) flattened, aperture, columella, and callosity fulvous. 

 Length 4, breadth 2 mill. 



Halntat, Sorell, a somewhat solid shell with much the habit 

 of a small Littoriua. 



PLANORBIS. GUETTARD. 



(Do la Classification des Coq. Paris 1756.) 



Testa discoidea, apira depressa vie prhninida ; anfractihus omnibus 

 utriiupie conspicuis, apertiira ohlowja, lunata, ab axe remotissinm ; 

 nmrginc numqnam rejiexo ; operculum nullum. 



Shell discoid, compressed, spire scarcely prominent, whorls 

 all visible on both sides. Aperture oblong, remote from the 

 axis, margin never reflected, no operculum. 



Freshwater shells of world-wide distribution. The species 

 also have a wide range. More than 100 are known and they 

 are very abundant in America. The variations from the typi- 

 cal form are not numerous. There are two or three known in 

 Australia but only one in Tasmania, and this appears to have 

 escaped previous observers. 



1. Planorbis TA.SMANICUS n.s. P. discoidea,minuta,planata, tenuis, 

 snpcnie convcxa, infcnic umbilicata, confertim sinuato - striata, 

 nitida, pellxicida, jmllide cornea, anfractibus (4 — 4i) convexis, ad 

 baslm ddatatis ; suturaprofunda; apcrtura ovata, obliqua ; peristonui 

 simplex slmuito. Uiam. vmj. 5, alt. 1, min. 3^ mil. 



Shell discoidal, minute, flattened, thin, convex above, umbil- 

 icate below, thickly sinuately striate, shining pellucid, pale 



