72 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



Distribution: Gulf of San Jorge, Patagonian beds (v. Ih.). Specimens 

 sent by v. Ihering to the U. S. Museum and examined by the writer were 

 labelled : Santa Cruz. 



Affinities: The most closely allied species, R. nigricans, has been found 

 living at New Zealand, and fossil in the Oamaru, Pareora and Wanganui 

 beds of New Zealand, and thus it ranges from the Oligocene upward to 

 Recent times. 



16. RHYNCHONELLA SQUAMOSA Hutton. , 



PI. XII, Fig. 4-. 



1873 Rhynclwnella squamosa Hutton, Cat. Tert. Moll; Echin., New Zea- 

 land, p. 37. 

 1878 R. ccelata Tenison-Woods, Journ. Proc. Roy. Soc. N. S. Wales, v. 



ii, p. 77. 

 1880 R. squamosa Tate, in: Trans. Proc. Roy. Soc. S. Australia, v. 3, p. 



1 66, pi. 9, f. 9. 

 1880 R. nigricans var. pixydata Davidson, Challenger Brach., p. 59, pi. 



4, f. 14. 

 1887 R. nigricans var. pixydata Davidson, in: Trans. Linn. Soc., ser. 2, 



v. 4, p. 170, pi. 24, f. 10. 



1896 R. squamosa Pritchard, in: Proc. Roy. Soc. Victoria, v. 8, p. 143. 

 1900 R. sqtiamosa Ortmann, in: Amer. Journ. Sci., v. 10, p. 378. 



Shell more or less transversely circular ; beak acute and incurved. For- 

 amen small. Dorsal (small) valve convex, mesial fold scarcely distin- 

 guishable. Ventral valve flatter, with a broad, well-defined mesial sinus. 

 Surface of both valves with about 40-50 radiating ribs, 10-15 of them in 

 the sinus ; closely intersected by squamose, concentric lines of growth, 

 giving an imbricated appearance to the surface. 



Length 24, 25, 25 mm. 



Width 26, 28, 26 mm. 



Remarks: Davidson confirms the identity of R. cczlata with his R. pixy- 

 data, and as Tate points out R. ccelata is distinguished from R. nigri- 

 cans by the same characters .that distinguish R. squamosa, being accord- 

 ingly the same as the latter. 



Our individuals agree well with the figures of R. squamosa, as well as 

 of R. pixydata, especially in the squamose surface markings. The only 



