PROCEEDINGS OF THE PERTHSHIRE SOCIETY OP NATURAL SCIENCE. 
73 
bivalves are difficult to distinguish from each other, 
especially as they are frequently coated with an algoid 
growth, or stained with iron and manganese. Their 
most reliable character is the contour of the shell ; 
the first-named species being the most triangular, the 
second more oval, and the third nearly round. All are to 
be found in the mud of stagnant pools, some of which 
should be put in a canister to be examined at leisure. 
Any one may find them in abundance by examining the 
pools of Methven Bog in this way. The variety pul- 
chella of P. fontinale, which well deserves its name, is 
not uncommon. 
5. TJnio margaritifer. As I described this most in¬ 
teresting species pretty fully last session, I need only 
say that it inhabits the Tay and nearly all its tribu¬ 
taries, as well as a number of the Highland lochs. 
The varieties sinuata and Roissyi both occur in the Tay. 
6. Anodonta cygnea was first discovered in Perthshire by 
Mr W. Herd, who detected some specimens both of the 
type and of the variety -incrassata. in a pool of the River 
Earn in 1869. It has since been taken in a pond near 
Dupplin Castle by Mr P. Smith, and in Scone Pond by 
Dr Buchanan White, who, it will be remembered, re¬ 
corded his find two years ago. 
7. Valvatapiscinalis has been found in rivers, lochs, and 
ponds in the lowland part of the country, where it is not 
uncommon. 
8. Planorbis nitidus. I have not found this species my¬ 
self, but have some specimens taken by Dr Buchanan 
White in ponds near Perth, where it was observed by 
him in 1870. 
9. P. nautileus is recorded by Mr J. Dawson from Old 
Scone, and has been found by Dr Buchanan White at 
Moncreiffe. 
10. P. albus is the most widely-distributed of the genus, 
particularly in the Highlands, where it inhabits ponds at 
considerable altitudes. It is easily distinguished by its 
dull white aspect, and by its strongly-marked striae. 
11. P. vortex. This beautiful little shell has only, I 
believe, been taken at Errol and near Dunning. 
12. P. contortus is common throughout the district, and 
may be known by its closely-coiled whorls. 
13. Physa hypnorum was detected as a Perthshire 
species by Mr J. M ‘Pariane, who discovered it at Errol 
in March, 1870. 
14. P. fontinale, which is to be distinguished from the 
preceding species by its much shorter spire, is found in 
most ponds and slowly-running streams throughout the 
county. The shell varies much, both in size and thickness, 
and in the height of the spire.. 
15. Limnaa peregra. This is at once the commonest and 
the most variable of our freshwater shells. Pew pools or 
sluggish streams are without specimens of it. Jeffreys de¬ 
scribes fourteen varieties of this species, of which about 
half may be found in the county. The finest specimens I 
have taken were from some of the dead-waters or old 
channels of the River Earn. 
16. L. palustris has a pretty wide range in the district, 
but is nowhere abundant. The shell is very handsome, 
and differs from that of the preceding species in its thick 
texture, prolonged spire, and dark olive or'horn colour. I 
have found the variety elongata not uncommon, and have 
seen fine specimens of the variety decollata gathered by 
Dr Buchanan White at Dunkeld. 
• 17. L. truncatula occurs in many localities. It 
appears to be partial to ponds at elevated situations, 
where, however, it seldom attains its full size. The 
shell differs from that of the preceding species in 
being much smaller, and having the sutures (or lines 
of junction between the whorls) deeper. Though an 
aquatic species, I was surprised to see some specimens of 
this little mollusc crawling on a dry bank in Quarrymill 
Den, at a considerable distance from the stream, but I 
have since found that it not unfrequently assumes an am¬ 
phibious habit for a time, in order to deposit its spawn 
upon the banks. 
18. L. glabra was added to the Scottish list by Dr 
Buchanan White, who discovered it in some small pools 
on the Muir of Durdie. Plow it was introduced into 
this lonely habitat is a problem not easily solved. 
19. Ancylus fluviatilis. This limpet-like mollusc gener¬ 
ally chooses running streams for its habitat, where, unlike 
other freshwater snails,,it is in no danger of being swept 
away by the current, but sticks fast to the stones by 
means of its broad muscular foot. It is common through¬ 
out the district in suitable situations, but is frequently 
overlosked, as the shells are easily mistaken for little 
heaps of mud adhering to the stones. 
20. A. lacustris occurs in some of the dead-waters of 
the River Earn near Dupplin, and at Moncreiffe, where 
it was first discovered by Dr Buchanan White. It is 
found adhering to the smooth stems of the iris and reeds, 
and is at once distinguished from the preceding species 
by its oblong shape. The variety albida occurs in the 
same place. This completes the list of aquatic species. 
With regard to the land mollusca I may remark that if 
any member wishes to make acquaintance with them for 
himself, he has ample opportunity of doing so in this 
neighbourhood, for a few excursions to Kinnoull and Mon¬ 
creiffe Hills will reveal a large majority of the species yet 
