IO6 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. 



to be correct, the name of O. rostrata of Hupe antedates O. ingens of 

 Zittel, and should be used accordingly. 



0. transitoria of Hupe (Philippi, p. 213, pi. 49, f. 9), from Coquimbo, 

 Caldera and Navidad (Pliocene and Miocene of Chili) may also belong 

 here. It is very broad, but agrees in this character with many individuals 

 from Patagonia. O. transitoria of Moericke (1896, p. 576, pi. 12, f. i), 

 however, seems to belong to O. patagonica (see below). 



Lately, several species of Ostrea have been described by Grzybowski 

 (1899, pp. 629-631) from the lower Miocene and Pliocene of northern 

 Peru (Payta and Tumbez), of which O. latiareata (Miocene) and O. oculata 

 and lunaris possibly also belong here. At any rate, they are closely 

 allied to O. ingens, but the material described and figured is too poor to 

 form an opinion upon. 



I shall now proceed to give a record of our specimens, adding under 

 each locality the necessary notes, which would serve to support the views 

 set forth above. 



Record of specimens : 



1. Mouth of Santa Cruz River; 12 double, 7 lower valves. 



One of them is my type of O. hatcheri. 2 more of the double valves 

 agree completely : they are broad, with distant lamellae. In 2 more the 

 lamellae are more crowded near the lower margin ; i other is a little 

 elongated, with crowded lamellae in the posterior third of the shell, other- 

 wise like O. hatcheri. 5 are very large, greatly elongated (one of them 

 figured on pi. XV and XVI), with the beak and area more elongated ; one 

 of them with distinct lateral furrows as in O. ingens from New Zealand ; 

 the lamellae are much crowded in the posterior part of the shell, i 

 further specimen is of medium size and elongated ; the lamellae are 

 crowded, except near the beak ; the area is long. Of the single valves 5 

 small or medium sized are the typical O. hatcheri ; form circular or 

 broadly oval. 2 others are larger and more elongated, one of them very 

 large, is very elongate, with the lamellae crowded in the posterior half; area 

 long and broad, with distinct lateral furrows. The other is a little smaller 

 than this one, ovate, the area triangular, the lamellae crowded posteriorly. 



In all specimens from this locality the radial ribs of the surface are only 

 slightly or not at all developed. 



As will be noticed, the typical O. hatcheri is represented, among these 

 19 individuals, by only 8. The rest are transitions to O. philippii, and a 

 few may be called O. philippii. 



