12 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 



These Chilean specimens are distinctly exogyrate and have very little re- 

 semblance to the Patagonian form. In a later work by Coquand * they 

 are referred to Ostrea a<]iiila, which is also made to include Exogyra im- 

 bricata Krauss, a similar form from the Uitenhage beds of South Africa. 



A species that resembles O, tardensis more closely than those above 

 mentioned has been described by Stoliczka 2 under the name Gryphaa 

 an'aua from the Arrialoor group of the Indian Cretaceous. Judging from 

 the figures the principal difference is in the somewhat less strongly curved 

 form of G. ariana. 



It is possible, though I think not probable, that the Patagonian Ostrea 

 here described as new is specifically identical with some of the South 

 American forms that have been referred to Exogyra coulom, but even if 

 that should prove to be true, the identification of that species is believed 

 to be erroneous in those cases and a new name is necessary. 



Locality and position. Mouth of canon of Rio Tarde, four miles east 

 of Lake Pueyrrydon, from a horizon (Gio beds) 400 feet below the Ammo- 

 nite layer. 



LIMA sp. 



Shell small, ovate, slightly oblique, convex with prominent beaks and 

 small inconspicuous ears; surface marked by about 15 rather prominent 

 radiating ribs about equal in width to the interspaces, each of which bears 

 a fine line. The anterior and posterior portions of the shell not covered 

 by the ribs also bear a number of fine radiating lines and show irregular 

 lines of growth. 



The"three imperfect specimens in the collection are probably immature, 

 the largest measuring only seven millimeters in length and five milli- 

 meters in breadth. 



Locality and position. From the Ammonite (Belgrano) beds at mouth 

 of canon four miles east of Lake Pueyrrydon. 



PECTEN (CAMPTONECTES) PUEYRRYDONENSIS sp. nov. 



Pi. IV, Fig. i. 



Shell of medium size, ovate or subcircular in outline, moderately con- 

 vex ; right valve with unequal ears, the anterior one much larger, trian- 



1 Monographic du Genre Ostrea, p. 158. 



'Cretaceous Fauna of S. India, vol. 3, p. 465, pi. 43, figs. 2, 2 a , pi. 44, figs. 1-3. 



