NO. 5 RHYNCHONELLOID BRACHIOPODS — COOPER 45 



Pedicle valve interior without dental plates. Other details not 

 known. 



Brachial valve interior with short crura and with the inner hinge 

 plates thickened and filling the intercrural space. 



Type species (by original designation). — Rhynchonella patagonica 

 von Ihering, Anal. Mus. Nac. Buenos Aires, ser. 3, vol. 9, t. 2, p. 334, 

 pi. 3, figs, na, b, 1903. 



Comparisons. — Patagorhynchia is comparable to two genera from 

 the Southern Hemisphere: Tegulorhynchia and Aetheia. The first 

 genus is ornamented like Patagorhynchia but there the similarity 

 ends because the South American genus has completely different beak 

 characters and the interiors are wholly unlike. Close comparison is 

 possible with Aetheia on the inside and in beak characters but Aetheia 

 is a smooth shell and externally not to be confused with Patago- 

 rhynchia. The Argentine shell has the minute foramen and concave 

 deltidial plates like the New Zealand shell. Inside the pedicle valve 

 no dental plates were observed in Patagorhynchia. The interior of 

 the brachial valve is not well known and the published illustration 

 of it is poor. It does indicate, however, cardinalia with moderately 

 long crura, concave inward, probably of falcifer type and a thicken- 

 ing of the inner hinge plates to fill the posterior space between them 

 with shell substance. The illustration indicates a condition even more 

 extreme than that seen in Aetheia. 



Geological horizon. — Eocene (Patagonian). 



Distribution. — Argentina and Chile. 



Assigned species. — Only one species, the type of the genus, is 

 known. 



Discussion. — Allan (1938) discussed the interior details of Pata- 

 gorhynchia, especially those of the pedicle valve. Specimens of 

 pedicle valves in the Canterbury Museum enabled him to determine 

 some characteristics not before seen, such as the strong concavity of 

 the deltidial plates and the fact that they do not exhibit the suture line. 

 He also described the great thickening formed by coalescence of the 

 deltidial plates with a platform made by a thickening at the base of 

 the teeth. 



Family HEMITHYRIDAE Rzhonsnitzkaia 1956 



Genus HEMITHYRIS d'Orbigny, 1947 



Plates 3, A, B, 4, E 



Hemithiris d'Orbigny, Paleont. France Ter. Cret., vol. 4, p. 342, 1847; Hertlein 

 and Grant, Publ. Univ. California at Los Angeles, Math, and Phys. Sci., vol. 

 3, p. 41. 1944- 



