152 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 



Length, 11 mm; height 7.5 mm; diameter (of right valve), 2.5 mm. 

 Cast from San Julian : length, 13 mm; height, 8 mm; diameter (double), 

 5 mm. 



Remarks: So far no Corbula has been known from Patagonia. In C. 

 birostris Phil., from Lota, Chili (Navidad beds), the genus is very doubtful. 



Record of specimens: Mouth of Santa Cruz River, 8 double, 6 right, 8 

 left valves ; Las Salinas, i left valve ; Mt. of Observation, upper horizon, 

 i left valve ; San Julian, Darwin Station, 2 double casts. 



Affinities: The most closely allied form, in my opinion, is C. subcequi- 

 valvis Sandb. (see: Boettger, 1870, p. 41, pi. 9 (8b), f. 16), from the Oligo- 

 cene of Germany and Switzerland. In C. hatcheri the posterior truncation 

 is less distinct, the lower margin is more arcuate, and the ribs of the sur- 

 face seem to be stronger (Boettger calls them "thin" in C. subccquivalms}. 



There are also some Miocene species of Europe and North America, 

 which might be compared with C. hatcheri, but they do not approach it 

 so closely as C. subcequivalvis. 



Fam. SAXICAVID^E. Gr. 



Gen. PANOPEA Men. 

 81. PANOPEA IBARI Philippi. 



PI. XXIX, Fig. 5. 



1887 Panopcea ibari Philippi, Tert. & Quart. Verst. Chiles, p. 167, pi. 35, f. 4. 

 1899 Glycimeris ib. Ortmann, in : Amer. Journ. Sci., v. 8, p. 429 (non Gly- 

 cimeris ibari (Phil.), see above, p. 94). 



Shell elongate-oval, moderately convex, with concentric undulations. 

 Apex at two-fifths of the length, prominent. Both ends rounded, poste- 

 rior distinctly narrower than anterior. Ventral margin arcuate. 



Length, 84 mm; height, 45 mm; diameter, 15 mm; apex at 35 mm 

 from anterior end. Rel. H. : L. = i : 1.8; in another individual : = i : 2.0. 



Record of specimens : Punta Arenas, lower horizon, II (lower Magella- 

 nian), i double, 2 right, 2 left valves. 



Distribution: Magellanes and Skyring Water (Phil.). 



