THE MOLLUSCAN FAUNA OF TASMANIA, 47 
not be assigned to them. Hence it frequently happens that the 
definition of a group is applicable to a few genera only, which 
its type, and does 
ieee that the plan of nature is followed when that she is 
confessedly ci ae a gp Indeed it ges a, t pgs the 
admired natural method of one differs from the censu 
ficial method of fear be merely in the aiteediones yd different 
systems of organs have been made choice of as the 
- respective classifications. Unless zoologists in “the forma- 
their primary groups endeavour to determine those 
pee which all the members possess in name mit 
only such marks into the de apie and practise the same 
as the euisivauan: of the science are num 
I now proceed to give a brief view of the Molluscan sub- 
kingdom as it affects Tasmania. 
Class, CeEPHALOPODA. 
Argonauta, Spirula, Sepia, &e. I do not enter into detail in 
this matter, as absolutely next to nothing has been done towards 
their classification in Tasm 
Class, GASTEROPODA ; pie Proso-BRANCHIATA ; Sub-order, 
PROBOSCID ; Famil URICIDE. 
Shell thick, with numerous scaly spiniform projections, and 
more or less wae — or spines ; ‘operculum oval, oblong; 
nucleus apical. 3, Typhis 1, i. Tephon 9, Fusus 6, 
honalia 5. 
2nd Family, PLevROTOMIDs. 
Animal, with a posterior slit in the mantle corresponding t 
— in the shell, and a straight siphon. Shell turriculate, with 
operculum horny; odontophore, two lateral series of 
tcash only. sive setaray 1, Drillia 7, Clathurella 2, Mangelia 9, 
Daphnella 
Family, Trrronip 2. 
Animal : Head large; foot short, thick, truncated in front ; 
adentophore 7, only 3-1-3; Spcennn horny, oval, oblong : b 
us subapical. ell ridged, with irregular mario Triton 
5, 3 Paitin 1, Ranella (varices cag a 3, Fipagia.l 
