356 A. E\ Ortmann — Oysters of Patagonia. 



2. Ostrea philii^pii nov. nom. (Plate XI, fig. 2.) 



Ostrea hourgeoisi Pliilippi, 1. c, p. 207, pi. 48, fig. 3. 



This species is characterized by its elongate-ovate form and 

 its elongate-triangular area. It attains a considerable size and 

 thickness (length, 236 mm ; breadth, 130 mm ; thickness, ca. 110 mm ), 

 and may have been also mistaken for 0. patagonica. In our 

 specimens the beak of the lower valve is longitudinally in- 

 curved, and in a few specimens this curve is very strongly 

 pronounced. 



I do not believe that this species is identical with the true 



0. hourgeoisi from the Californian Pliocene (Remond, Proc. 

 Calif. Ac, 1863, p. 13, and^ Gabb, Geol. Surv. Calif. Pal. ii, 

 1869, p. 33, pi. 11, fig. 57), since the most important character 

 of the latter, the constriction of the shell near the cardinal 

 area, is not represented in Philippi's figure, and is not exhibited 

 by any of our specimens. 



Localities : Very abundant in the Supra-Patagonian beds of 

 Upper Rio Chalia and at Shell Gap on Upper Rio Chico. 

 Philippi quotes it from Punta Arenas. 



3. Ostrea patagonica d'Orb. 



d'Orbigny, Yoy. Amer. Merid. Pal., 1842, p. 133, pi. 7, fig. 14-16. Philippi 



1. C, p. 205, pi. 48, fig. 2. 



This species differs from O. pkilippii by its subtriangular 

 (not ovate) outline and the shortness of the beak and area. 



0. patagonica seems to be restricted to the more recent beds 

 of the South American Tertiary, since d'Orbigny's types are 

 from Entre Rios, and most of the other localities given by him 

 are situated in the northern parts of Argentina, where the 

 older (Eocene or Miocene) beds seem to be absent. There has 

 been much confusion as to this fossil, since almost all large 

 oysters found in Patagonia have been called by this name. 

 But in the true Patagonian beds and in the Supra-Patagonian 

 beds O. patagonica is entirely wanting, 0. hatcher i and pkil- 

 ippii having taken its place. 



There are numerous specimens of a large oyster in our col- 

 lection from the probably Pliocene Cape Fairweather beds, 

 which resemble very closely O. patagonica^ but the muscular 

 impression in all our specimens is situated nearer to the pos- 

 terior margin of the valve than in d'Orbigny's figure. This 

 Cape Fairweather oyster may be identical with 0. patagonica 

 or may represent, as Mr. Pilsbry believes, a new species ; at 

 any rate, it is closely allied to O. patagonica. 



I present here a comparative plate giving the internal views 

 of the lower valve of our types of O. hatcheri and philippii, 

 as well as the reproduction of the original figures of 0. hour- 

 geoisi (pi. XI, fig. 3) combined from Gabb's fig. 57 a and 57 b 

 (on pi. 7, 1. c), and a copy (pi. XI, fig. 4) of d'Orbigny's 

 original figure of 0. patagonica (1. c, pi. 7, fig. 14). 



