ORTMANN I TERTIARY INVERTEBRATES. 149 



Fam. PSAMMOBIIDsE Ball. 



Gen. PSAMMOBIA Lam. 

 76. PSAMMOBIA PATAGONICA Philippi. 



PI. XXIX, Fig. 4. 



1887 P. pat. Philippi, Tert. and Quart. Verst. Chiles, p. 143, pi. 26, f. 17.' 

 1899 P. pat. v. Ihering, in: N. Jahrb. Miner., etc., v. 2, p. 21. 



Shell elongated-elliptical, compressed, smooth, almost equilateral, the 

 posterior end a little shorter, both ends evenly rounded. Anterior and 

 posterior dorsal margins straight, forming an obtuse angle. Ventral 

 margin very slightly curved. 



Length, 28 mm; height, 16 mm; diameter, 3 (x 2) mm. 



Record of specimens : Mouth of Santa Cruz River, 10 valves; Las 

 Salinas, 6 valves ; 30 miles north of upper Rio Chalia, i double cast ; 

 Arroyo Gio, 3 casts. 



Distribution: Patagonian beds of Santa Cruz (Phil., v. Ih.). 



Affinities : This species has a distinct Eocene appearance, and resembles 

 much the forms described by Deshayes (1860, p. 370, ff.) under the names 

 of P. nitida (pi. 24, f. i, 2), and P. tenera (pi. 24, f. 6-8), especially the 

 first, with which it also agrees in size. 



A very closely allied species is P. hamiltonensis Tate (1887, p. 167, pi. 

 1 6, f. 13) from Muddy Creek, Victoria, and Table Cape, Tasmania, from 

 so-called "Eocene," but probably Miocene beds. 



Fam. MACTRID^. Gray. 



Gen. MACTRA L. 

 77. MACTRA (?) DARWINI Sowerby. 



PI. XXIX, Fig. 8. 



1846 M. d. Sowerby, in : Darwin Geol. Observ. S. Amer., p. 249, pi. 2, f. 9. 

 Shell triangularly subovate, almost equilateral, compressed, but con- 

 vex toward the apex. Surface smooth, with concentric lines of growth. 



'There arc two figures numbered 17 on Philippi's plate, but only the smaller one represents 

 this species, the larger one is Tcllina subfalcata. 



