NATURAL HISTORY OF THE BANKS OF THE TAY. 61 
years. The pearls vary in colour from pure white to deep brown, and 
are sometimes beautifully iridescent.* 
Dreissena polyinorpha, Pallas.—This species used to be fairly 
common at the Old Harbour, where it was supposed to be introduced 
on teak logs. I am not aware whether it has spread farther up the 
river. 
Valvata piscinalis, Mull.—Occurs sparingly where the current is 
not strong. 
Flanoi'his albus^ Mull., and P. Contortus^ L.—Common in ponds 
and ditches. 
P. voi'tcx^ L.—Has been taken at Errol. 
Physa hypnoriim^ L.—Also taken at Errol, by the late Mr. 
J. M‘Farlane, in 1869. 
P. fontinalis. —North Inch Pond. 
Limncea peregra^ Mull.—Common throughout the lower part of 
the course of the river, where the current is not so strong, also in 
ponds, &c. 
Z. palustris. —With the last, but not so common. The varieties 
decollata and elongata both occur in the Tay near Perth. 
Ancyhis fluviatilis^ Mull.—On stones at the edge of the river in 
several places. 
Of the Limacida (Slugs), several species must be common on the 
haughlands, but, as no special search has been made for them in this 
area, it will be better not to include them in the present list. 
Succinea piitris^ L.—In damp situations overhanging the river 
in several localities. 
Vitriiia pellucida^ Mull., Zonites cellarius^ Mull., Z. alliarius^ 
Miller, Z. nitidulus^ Drap., Z. purus^ Aid., Z. radiatulus^ Aid., Z. 
crystallhius, Mull., and Z. fiilvus^ Mull.—These all occur amongst 
moss, loose stones, and long grass in moist and shaded situations on 
the banks of the river. Z. cellarius sometimes attains an exceptional 
size, as at Stormonfield, on the bank between the river and the lade. 
Of Z. piirus the variety margaritacea is as common as the type. 
Z. radiaiitlus is the rarest of the genus, having only been got at one 
or two stations. 
Helix aspersa^ Mull.—On rocks at the foot of Kinnoull Hill, not 
far from the river. This is a rare shell in the county. 
H neinoralis^ L., and H. arbustorum^ L.—Both fairly common 
and widely distributed, especially the former. 
* A detailed account of the Pearl Mussel of the Tay, by the present writer, 
will be found in the Proceedings for 1882, p. ii. 
