ORTMANN : TERTIARY INVERTEBRATES. 143 



1898 Meretrix iheringi Cossmann, in: Rev. crit. Paleozool., v. 2, No. 3, 

 p. 109. 



1899 Cytherea ih. Ameghino, in: Segundo Censo Arg. Supl., p. 4. 

 Shell large, swollen, with concentric sulci. Apex slightly prominent, 



at y^ of the length of shell. Anterior dorsal margin straight, posterior 

 slightly arcuate. Anterior end of shell shorter, rounded ; posterior sub- 

 rostrate. Lunula circumscribed by a slightly impressed line. Three car- 

 dinal teeth ; the anterior and middle one diverging from the apex. Lateral 

 (lunular) tooth of left valve strong, lamellifonn, and parallel to the 

 lunula. 



Remarks: We possess only an incomplete left valve, but it agrees 

 according to the lines of growth with this species in form. The hinge 

 is well preserved, and corresponds well to the description given by v. 

 Ihering: especially the large lunular tooth is very striking. 



Record of specimens : Punta Arenas, horizon V (Patagonian); i left valve. 



Distribution: Jegua quemada and La Cueva, Suprapatagonian beds 

 (v. Ih.). 



70. MERETRIX ROSTRATA (Koch). 



PI. XXVIII, Fig. 6. 



1845 Cytherea rostr. Koch, in: Philippi, Abbild. neu. Conchyl., v. i, p. 

 150, pi. i, f. 3. 



Shell cordate-ovate, oblique, swollen ; surface with concentric lines of 

 growth. Apex much produced and strongly incurved. Anterior end of 

 shell short, rounded ; posterior longer, rounded and a little produced. 

 Lunula very large, cordate, almost flat, circumscribed by a distinct im- 

 pressed line. Pallial sinus triangular. 



Height, 34, 39 mm; length, 38, ca. 42 mm; > diameter (of first speci- 

 men), ca. 14 mm. 



Remarks: Our material consists chiefly of casts, but some show large 

 portions of the shell preserved. The agreement with the recent form is 

 complete. The outline of the shell is a little variable, the apex being 

 more or less produced. 



Record of specimens: Cape Fairweather; remains of 14 valves. 



Distribution: So far known only Recent from Brazil (Koch); I have 

 seen, in the collections of the Academy of Philadelphia, specimens from 

 Maldonado Bay, Uruguay. 



