ORTMANN : TERTIARY INVERTEBRATES. 85 



terminates," which taken together with his figure applies well to our 

 species. 



Record of specimens : Mouth of Santa Cruz River, i left valve; Cafion 

 near Sierra Oveja, Rio Chico, 100-150' below the rest, i cast; Arroyo Gio, 

 i external cast; Lake Pueyrredon, 600' above base, 15 sp. 



Distribution: Navidad beds of Chili, Lebu (Philippi). 



Affinities: Leda hyposoma Ball (1898, p. 589, pi. 32, f. 2)' from the 

 Miocene of North Carolina much resembles our species in the character 

 of the sculpture, the concentric lines disappearing on the rostrum and 

 leaving a smooth space below the ridge. Also the general form is similar. 

 This species is to be regarded as the most closely allied form. 



Species of Leda coming near L. oxyrhyncha and errazurizi are found 

 in the Australian Tertiary (Tate, 1886), but they require further exami- 

 nation owing to the poor figures. 



Gen. MALLETIA Desm. 

 26. MALLETIA ORNATA (Sowerby). 



PI. XXVI, Fig. 4. 



1846 Nucula orn. Sowerby, in: Darwin, Geol. Obs. S. Amer., p. 251, pi. 



2, f. 19. 



1854 Solenella orn. Woodward, Man. Mollusc, vol. 2, p. 270, pi. 17, f. 23. 

 1899 Neilo orn. v. Ihering, in : N. Jahrb. Min. Geol. Palaeont., vol. 2, p. 14. 



Shell large, elongate, ovate or subtrapeziform ; apex only slightly prom- 

 inent, at about two-thirds of the length of the shell. Anterior end rounded, 

 posterior obliquely truncate and emarginate, upper angle produced, lower 

 angle rounded. A blunt angulation running from the apex to the lower 

 angle, and a very indistinct angulation from the apex almost parallel to 

 the posterior dorsal margin. Surface with strong, lamelliform, concentric 

 ribs. Anterior hinge teeth ca. 15, number of posterior teeth a little larger 

 (the exact number cannot be ascertained in our specimens). 



Length, 45 mm ; height, 25 mm. 



Remarks: Ligament external in a longitudinal groove, and pallial line 

 with a distinct sinus, thus belonging to the genus Malletia of Desmoulins 

 ( = Solenella Sow. = Neilo Ad.). 



Record of specimens : Mouth of Santa Cruz River, i double valve, 2 

 right, and 2 external casts ; Paso del Rio Santa Cruz, i left, 3 right valves. 



