ORTMANN : TERTIARY INVERTEBRATES. 145 



other. But in D. semilcems they appear still more widely distant than in 

 D. magellanica, and the outline of the shell is different. 



72. DOSINIA MERIDIONALIS V. Ihering. 

 PI. XXIX, Fig. 2"- c . 



1897 D. m. v. Ihering, in: Rev. Mus. Paul., v. 2, p. 256, pi. 6, f. 41. 



Shell circular, compressed ; posterior dorsal margin forming, with the 

 posterior margin, a strong curve, giving the appearance of a blunt and 

 indistinct angle. Lunula concave, oblongo-cordate, its margin obtuse and 

 indistinct. Surface with concentric impressed lines, which are somewhat 

 irregular (more or less deep, and more or less widely distant), on the 

 whole quite crowded ; the intervals between these lines are distinctly con- 

 vex, but not much so. 



Measurements : Length, 55 mm; height, 51 mm; diameter (double), 

 23 mm. V. Ihering gives the following measurements: Length, 83 mm; 

 height, 74 mm; diameter, 21 (x 2) mm, but his figure is much smaller. 



Remarks : V. Ihering says that the concentric sculpture tends to become 

 obsolete in the middle of the shell : in his figure it is quite distinct every- 

 where, and is also in our specimens well developed in the middle. Toward 

 the margins the sculpture becomes more strongly pronounced. 



Young individuals, about as large as D. magellanica, differ at once 

 from the latter in the concentric lines' being more crowded, and the 

 intervals' being distinctly convex. 



. The casts from upper Rio Chalia do not show any details of sculpture, 

 but agree at least two of them completely in outline. The internal 

 cast from Cape Fairweather is very poor, but the cast of the surface 

 sculpture, as well as the size and form of the pallial sinus agree with 

 this species. 



Record of specimens: Mouth of Santa Cruz River, 2 double, 7 right, 5 

 left valves ; Upper Rio Chalia, 6 casts ; Arroyo Gio, i double valve ; 

 Cape Fairweather, i inner cast of right valve, and part of external cast 

 of right valve. 



Distribution: Jegua quemada, Suprapatagonian beds (v. Ih.). 



According to v. Ihering (1897, P- 33 this species is also found in the 

 "Paranense" formation of Parana, Entrerios. As only casts have been 



