STANTON : THE MARINE CRETACEOUS INVERTEBRATES. 2$ 



ovate adductor muscle impressions. The pallial line is very faint and the 

 sinus not distinctly seen. 



Length of an average specimen 20 mm.; height 9 mm.; convexity of 

 both valves about 4 mm. 



This species closely resembles Solen cequalis d'Orbigny 1 which the 

 same author afterward referred to Solecurtus. It is smaller than that 

 species and not quite so slender. 



Locality and position. The figured specimen is from the Ammonite 

 (Belgrano) beds 10 miles east of Lake Pueyrrydon. It also occurs at the 

 locality four miles east of the lake, and is represented by about a dozen 

 specimens from the two places. 



PLEUROMYA LATISULCATA sp. nov. 



PI. VI, Figs. I and 2. 



Shell of medium size, oblong ovate, or subcuneate in form, the great- 

 est convexity near the front end midway between the beak and the ven- 

 tral margin ; anterior end broadly rounded, posterior end more narrowly 

 rounded and slightly gaping ; ventral margin very slightly convex ; dor- 

 sal margin descending abruptly in front of the beaks and rather rapidly 

 behind them ; beaks prominent, approximate, somewhat flattened, situated 

 near the anterior end of the shell ; a rather prominent broad ridge, on 

 which the sculpture is most strongly marked, extending from the beak al- 

 most vertically to the antero-ventral angle, a much more obscure pos- 

 terior umbonal ridge running obliquely to the posterior end, and the side 

 between these two ridges flattened ; surface marked by very prominent 

 concentric ribs separated by broader furrows, and the whole covered with 

 finer growth lines. 



Length, 38 mm. ; height, 25 mm. ; convexity of the two valves, 20 mm. 



Locality and position. From the Ammonite. (Belgrano) beds at mouth 

 of canon four miles east of Lake Pueyrrydon. Represented by a single 

 specimen. 



MACTRA (?) sp. 



Shell rather small, elongate, moderately convex, with prominent beaks 

 slightly in advance of the middle ; anterior end broadly rounded ; posterior 

 end narrow, obliquely subtruncate; ventral margin gently convex: an 



'Pal. Fr. Terr. Cret, t. 3, p. 321, pi. 350, figs. 5-7. 



