138 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



widely distant, elevated and sharp concentric lines, which are, toward the 

 ventral margin, more crowded ; besides, there are distinct radiating striae. 

 Margin of shell very finely crenulated. 



Length, 33 mm; height, 27 mm; another individual: Length, 31 mm; 

 height, 24 mm; diameter (double), 15 mm. 



Remarks: This species differs from V. chiloensis chiefly in the outline; 

 it is more elongated (rel. H.: L. = i : more than 1.2, while in V. chiloensis 

 it is = i : less than 1.2). Further, the position of the apex is different, 

 and the lunula is convex and distinctly elevated in the middle in V, 

 meridionalis. Young individuals, however, have a more circular outline. 



Record of specimens : Mouth of Santa Cruz River, 14 double, 57 iso- 

 lated valves ; Las Salinas, 3 isolated valves ; Mt. of Observation, upper 

 horizon, 2 isolated valves ; Shell Gap, Rio Chico, upper horizon, 2 casts ; 

 Lake Pueyrredon, 600' above base, 17 casts. 



Distribution: Patagonia'n beds of Santa Cruz (Sow., v. Ih.); Supra- 

 patagonian beds of Jegua quemada (v. Ih.); Navidad beds of Chili : Navi- 

 dad (Sow., Phil.), Ranquil near Ancud (Phil.). 



Affinities: A species similar in outline and sculpture is Mercenaria 

 cancellata Gabb (see: Whitfield, 1884, p. 68, pi. 12, f. 2, 3), from the 

 Miocene of New Jersey. It is intermediate in outline between V. merid- 

 ionalis and chiloensis. In V. clathrata Duj. (see Hoernes, 1870, p. 125, 

 pi. 13, f. 3), from the Miocene of Europe the same type of surface orna- 

 mentation is seen, but much more strongly developed. Moreover, V. cla- 

 thrata is much higher and more rounded than even V. chiloensis. 



This type of ornamentation in the genus JSenus (cancellated surface) is 

 characteristic for species from Miocene to Recent deposits. It is repre- 

 sented in Australia and Tasmania by V. multitceniata Tate (= mnltilamel- 

 lata Tate, 1887, p. 154, pi. 15, f. 6), and V. hormophora Tate (ibid., p. 155, 

 pi. 15, f. i), said to be Eocene, but being probably Miocene. 



According to Hutton (1886, p. 362), Cliione uellicata Hutt. (1873, p. 

 21), is identical with V. meridionalis, and thus this species would also 

 belong to the Pareora and Wanganui beds of New Zealand. 



