DESCRIPTION OF NEW SPECIES 

 Pelecypoda 



GENUS NUCULA LAMARCK 

 NUCULA WASHINGTONENSIS n. sp. 



Plate III, Figures 27, 28 and 29 



Description Shell very small, thick and robust; triangular outline; beaks 

 small, low and decidedly incurved anteriorly. Posterior cardinal margin decidedly 

 convex and very slightly truncated at the posterior end; anterior dorsal margin 

 slopes downward from beaks at an angle of 60 and is somewhat concave; basal 

 margin broadly arcuate. Lunule cordate and deeply impressed and sculptured 

 by a faint continuation of the lines of growth from the valves. No radiating sculp- 

 ture is visible on any of the specimens examined. Shell material thick and exhib- 

 iting a pearly lustre. Surface marked by numerous very well developed lines of 

 growth. This species is characterized by its small size and great thickness. 



Dimensions Altitude 7 mm. ; longitude 9 mm. ; thickness 5 mm. to 6 mm. 



Occurrence At locality 230 (University of Washington Palaeontological 

 Collection) situated in a railway cut on the North River branch of the Chicago, 

 Milwaukee & St. Paul Railway about two miles south of its junction with the 

 Grays Harbor branch in Section 29, Township 17 North, Range 8 West. 



Horizon Lower Miocene; Area montereyana Zone. 



GENUS LEDA SCHUMACHER 



LEDA WASHINGTONENSIS n. sp. 

 Plate III, Figures 25 and 26 



Description Shell of medium size, elongate and narrow; anterior dorsal mar- 

 gin two fifths the length of shell, nearly straight and sloping downwards at an 

 angle of 10 from the beaks; anterior end sharply rounded and merging into a 

 slightly arcuate base; posterior dorsal margin slightly concave and deeply exca- 

 vated ; posterior end rostrate and obliquely truncate. On both valves a nar- 

 row but distinct groove extends from beaks to posterior end which becomes 

 more deeply impressed near the latter. Surface of shell is sculptured by well 

 marked concentric ribs which are flat topped and with interspaces of about equal 

 width. Radiating ribs are absent. Beaks not very prominent; lunule linear and 

 marked by very faint incised lines ; escutcheon sunken, elongate-lanceolate, ex- 

 tending from beaks to posterior end and obliquely grooved with rounded outer 



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