364 APPENDIX. 
mark is left in those specimens which are of older 
growth, leaving a white callous-looking line of growth 
edged with brown, nearly in the centre of the last whirl, 
which is very large, being about four times the size of 
all the others put together. The two upper whirls, 
which are very small, are of a black colour. The sur- 
face of the shell is finely decussately striated. 
The Physa heterostropha of Say abounds in the 
Sumass Prairie, on the Fraser River; but its place 
seems to be taken on the higher ground towards the 
Rocky Mountains by the Ph. Lordi. Long. from ? to 
1 inch; lat. from 4 to ? inch. Hab. Lake se it 
British Columbia. (Brit. Mus.) 
Planorbis trivolvis. (Say.) Common west of the Cascades, replaced 
by P. corpulentis east. 
— corpulentis. Abundant in the Osoyoos lakes. 
Ancylus Kootaniensis. (Baird: Nov. Sp.) 
Testa ovata, cinerea, concentrice striata, vertice 
antico, obtuso; intus nitida. 
The shell is of an ovate form, and is concentrically 
striated, though the striae only appear on the lower 
two-thirds of its surface, the apex being smooth and 
shining. Internally the shell is shining and somewhat 
pearly. Long. } inch; lat. } inch.—Hab. Rivers Koo- 
tanie and Spokan. (Brit. Mus.) 
VENERID. 
Chione Lordi. (Baird: Nov. Sp.) 
Testa minuta, ovato-trigona, nitida, concentrice 
transversim sulculata, umbonibus prominulis, nitidis- 
