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 verv large, being about four times the size of 



/ ft * o 



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 

 Eocky Mountains by the Ph. Lordi. Long, from f to 

 1 inch; lat. from 1 to f inch. Hab. Lake Osoyoos, 

 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 stria3 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. ) 



VENERIM:. 



Chione Lordi. (Baird: Nov. Sp.) 



Testa minuta, ovato-trigona, nitida, concentrice 

 transversim sulculata, umbonibus prominulis, nitidio- 



