ORTMANN I TERTIARY INVERTEBRATES. 123 



Record of specimens: Lake Pueyrredon, base of Tertiary, i sp.; Lake 

 Pueyrredon, 400' above base, ca. 35 sp.; Lake Pueyrredon, 600' above 

 base, ca. 8 sp. 



Fam. CRASSATELLITID^E Ball. 



Gen. CRASSATELLITES Krueger. 



46. CRASSATELLITES LYELLI (Sowerby). 



PI. XXVI, Fig. 9". . 



1846 Crassatella I. Sowerby, in: Darwin, Geol. Observ. S. Amer., p. 249, 



pi. 2, f. 10. 

 1897 C. 1. v. Ihering, in: Rev. Mus. Paul, v. 2, p. 246. 



Shell obovate, comparatively thin and flat, rounded anteriorly, angu- 

 lated posteriorly ; posterior dorsal margin oblique, straight or slightly con- 

 cave near the apex ; anterior dorsal margin straight near the apex, hardly 

 concave. Surface with broad concentric grooves, which are separated by 

 blunt ridges. 



Length, 44 mm; height, 33.5 mm; diameter, 5.5 (x2). 



Remarks: V. Ihering says that the ventral margin is crenulated. I do 

 not see any crenulations in our specimens. 



Record of specimens: Mouth of Santa Cruz River, i double, i right, 3 

 left valves. 



Distribution: Santa Cruz (Sow.), Patagonian formation (v. Ih.). 



47. CRASSATELLITES KOKENI (v. Ihering). 



PI. XXVI, Fig. io"'*. 



1899 Crassatella k. v. Ihering, in: N. Jahrb. Miner., etc., v. 2, p. 17, pi. 

 2, f. 2. 



Shell ovate, subtriangular, comparatively thicker than in C. lyelli, and 

 more convex ; rounded anteriorly, angulated posteriorly, but not so much 

 produced as in C. lyelli. Posterior dorsal margin oblique, slightly con- 

 vex near apex; anterior dorsal margin distinctly concave below apex. 

 Surface markings nearly as in C. lyelli, but the ridges separating the con- 

 centric grooves are a little sharper. Ventral margin sharply crenulate. 



Measurements : Length, 26mm; height, 22 mm; diameter, 6 (x 2) mm. 



