T H E TA S M A NIA N N AT U R A LI ST. 
27 
Mitras are fairly well represented, and Marginellas are very numerous, 
Tasmania being rich in this genus. They are small, highly polished 
shells, inhabiting sand or mud from low water to 100 fathoms. 
7. The Cyprceida or Cowries, which owe their high polish to the 
size of the shell-secreting organ (mantle), whose edges meet over the 
back of the shell, concealing it within its folds. One large and several 
smaller species occur here. 
The second group, or Holostomata , is divided into nineteen 
families, beginning with— 
r. The Naticidic, whose type, Natica , is well represented by the 
common A 7 . conit a of our coasts (Fig. 9) 
2. The Cancel/arid(c, in which the shells are cancellated or cross- 
barred by a double series of lines. 
3. The Pyramidellidic , which are high spired, elongated and 
slender shells, usually small or minute forms. 
4. The Solar idcc or ‘ Staircase shells,' whose umbilicus is so wide 
that as you look down it the projecting edges of the whorls appear 
like a winding staircase (Fig. 8). 
5. The Scalar/'dee, which may be readily recognised from their 
white and lustrous appearance and from the strong ribs that encircle 
the whorls (Fig. 18). 
6. The Cerithiadce (or 4 Horn shells ’), very high spired (Fig. 13). 
These shells are usually dull coloured, and occur here in shallow, 
muddy bays and estuaries. 
7. The Turrilcllidcc or ‘ Tower shells/ the type Turritella (Fig. 
10) is spiral, but in the allied vermetns, though the spire begins in 
the natural manner, it goes off into a twisted tube, resembling some¬ 
what an ill-made corkscrew. The mouth of this family is often 
nearly round. All these forms are well represented here. 
8. The Mclaniadac, and 9, the Paludinidae , are mostly fresh¬ 
water shells; the former is not found here, but the latter is repre¬ 
sented by a species that is very abundant on mud flats in shallow 
inlets, where it is more or less amphibious. 
10. The Litorinidae or ‘Periwinkles' are small, round shells 
found living on stones at or near high water mark. 
11. The Calyptraedae comprise the ‘Bonnet limpets.' They 
may be described as limpets with traces of a spire left, several of our 
species live perched on other shells, either living or dead. 
12: The Turbinidae or ‘Top shells,’the common Turbo utidu - 
latus or. ‘ Warriner,' and the Phasianella, ‘ Pheasant shell ’ (Fig. 11) 
are examples with shelly operculums ; and Trochus with horny" oper¬ 
culums are well represented by some handsome species (Fig. 14), 
among them being the well known ‘ Kelp shell.' 
