74 CALIFORNIA ACADEMY OF SCIENCES. 



In the first table, one species (Camfylcea mormonum ) 

 is merely a straggler from the mild Californian region into 

 the subalpine, which indicates the lower limit of the sub- 

 alpine on the west slope to be between 4,000 and 4,500 

 feet, near latitude 38° ; and as the lowest level of the 

 Great Basin on the east slope is not much, if at all, below 

 4,000 feet, the whole of the basin region north of that 

 latitude is referable to the subalpine mollusc-fauna. 



In the last table, both this and Arionta tndiculata are 

 found on the west side, near the lower limit of the former 

 glaciers, and the Liinax also near their limit on the east 

 slope, but future collections may alter these ranges. 



As to the aquatic species the large supply of fresh wa- 

 ter in the Lake Tahoe basin causes apparently a great 

 increase of their numbers, and in both tables only the fol- 

 lowing are unknown below the subalpine region in the 

 same latitudes, viz., the planorbis, pompholyx, ancylus 

 and sphgerium. It is also noticeable that seven land 

 and ten water species have not been found in latitude 39° 

 above 6,500 feet (near Lake Tahoe), leaving but three 

 as yet known from the higher locations. Near latitude 

 38° there were sixteen species found between 6,500 and 

 9,700 feet altitude, partly on account of the nature of the 

 country being more favorable for their existence. 



The glaciated region extended over the lake basin, 

 having a total width of less than 40 miles, and the high- 

 est peaks are now less than 9,500 feet high. 



SpHyER-iUM RAYMONDi, n. sp., Plate I, figs. 1-8. Spec, 

 chars. Adult shell ovate trigonal, nearly equilateral, 

 much inflated, the greatest convexity near the middle, 

 fragile, translucent; beaks central, slightly turned for- 

 ward, very strongly calyculate; margins forming a subo- 

 vate outline, the anterior obtusely rounded, posterior usu- 

 ally obliquely subtruncate ; base curved equally with the 



