104 Kansas Academy of Science. 



and narrower than the ribs ; surface of shell covered with a minute 

 latticework where not worn off, also by conspicuous growth lines 

 near the margin ; anterior ear imperfectly ribbed with four to six 

 ridges, and showing elevated, concentric transverse ridges and in- 

 cremental lines ; posterior ear small, showing four ribs and con- 

 spicuous incremental lines ; left valve not seen. 



This shell differs from I^. ( Chlatnys) jo7'dani in that the shell is 

 larger and thicker, that its length and altitude are not the same, 

 and that the ribs of the right valve, the valve seen, do not become 

 dichotomous till they are about 45 mm. in length. 



Dimensions: Length, 55 mm.; alt., 55 mm. (measure of 56). 



Septifer bifercatus (?). Figure 6. 



The specimen given here is a fragment of the left valve. By a 

 careful comparison with identified specimens it was doubtfully 

 classed as above. Beds of these shells were found, but on account 

 of their long interment they all crumbled to dust on exposure to 

 the air. This fragment was saved with the greatest difficulty. 



Tapes staminea (Conrad), Figure 7. 



Arnold's description:" "Shell of medium size and thickness, 

 suboval, convex; surface sculptured with numerous crowded, 

 rounded, radiating ridges and concentric lines, which are most 

 prominent on the anterior end; no lunule; margin sometimes 

 crenulated; hinge narrow; ligament narrow, long; three teeth in 

 each valve; posterior two in right valve and middle one in left 

 valve bifed; pallial sinus long, rounded; muscle impressions not 

 sunken. 



" This is a variable species; the shape of the shell and the sculp- 

 ture varying in different individuals ..." 



Dimensions: Length, 20 mm.; alt., 14 mm. 



Living: Straits of Fuca to Lower California (Cooper). 



Pleistocene: Santa Barbara to San Diego, Cal. (Cooper); San 

 Pedro, San Diego, Cal. (Arnold). 



Pliocene: Santa Rosa; Twelve Mile House, San Mateo county, 

 Rirker's Pass, Contra Costa county, Monterey and San Fernando, 

 Cal. ( Cooper ) ; San Diego, Cal. ( Arnold ) . 



Miocene: West of San Jose; Foxin's, Santa Barbara county, 

 California (Cooper). 



7. Loc. cit.. p. 150. 



