258 WEST AMERICAN SHELLS 
shell is oval, obliquely conical, ribbed, the wedge- 
shaped puncture opening towards the shorter side. 
Internally a curved partition separates the pune- 
ture from the apex of the shell. The color is pure 
white within, dirty white without. My specimen 
from Monterey measures 28mm. in length and 14 
millimeters in height. 
Puncturélla coopert, Cpr., Cooper’s Puncturella, 
resembles C. galeatea, but the internal plate is 
Fig. 290 (*) 
solid and plane. Small, about 9mm. in length. 
Found at Catalina Island. 
Figure 290 represents two views of a notable 
shell, Subemarginula yatesu, Dall, Yates’ Trough- 
shell. A few specimens of this species were 
obtained by Mr. J. K. Oliver of Monterey, from the 
adjacent bay, one of which was secured by Dr. 
Yates, who forwarded it to Washington, where it 
received its name. The shell is large, strong, gray- 
ish-white in color, and has many radiating ribs. 
