ORTMANN : TERTIARY INVERTEBRATES. 
123 
Record of specimens : Lake Pueyrredon, base of Tertiary, 1 sp. ; Lake 
Pueyrredon, 400' above base, ca. 35 sp.; Lake Pueyrredon, 6oo' above 
base, ca. 8 sp. 
Fam. CRASS A TELLITIDAEL Dali. 
Gen. CRASSATELLITES Krueger. 
46. CRASSATELLITES LYELLI (Sowerby). 
PL XXVI, Fig. 9 0 ’ \ 
1846 Crassatella /. Sowerby, in: Darwin, Geol. Observ. S. Amer., p. 249, 
pi. 2, f. 10. 
1897 £ ^ 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 crenellated. I do 
not see any crenulations in our specimens. 
Record of specimens : Mouth of Santa Cruz River, 1 double, 1 right, 3 
left valves. 
Distribution: Santa Cruz (Sow.), Patagonian formation (v. Ih.). 
47. Crassatellites kokeni (v. Ihering). 
PI. XXVI, Fig. 1 o”’ 6 . 
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, 26111m; height, 22 mm; diameter, 6 (x 2) mm. 
