ORTMANN : TERTIARY INVERTEBRATES. 79 



Distribution: As has been mentioned above, some of the specimens 

 recorded by Lahille from the territory of Chubut (Pyramides, Madryn) 

 may belong to this species. A fragment of a large individual, with the 

 characteristic thickening of hinge and septum, has been sent by v. Ihering 

 to the U. S. Museum, and said to come from the "Tehuelche formation" 

 of Ameghino. Other younger individuals of the typical T. gigantea were 

 in the same lot, labelled (according to Ameghino) "Patagonian forma- 

 tion." But since Ameghino's views on the latter formation are very con- 

 fused, and since all his stratigraphical observations are second hand, it is 

 better to disregard the statement that these specimens are from the Pata- 

 gonian formation. 



Affinities: The comparative flatness of the dorsal valve, the generally 

 a little broader outline, and the very large size are the only characters 

 that distinguish this species from T. Patagonia, and there is no doubt that 

 it is the descendant of the latter, representing it in the Cape Fairweather 

 beds : it is a "mutation" of T. patagonica. In this respect it is interesting 

 to note that the broader variety of T. patagonica prevails at the localities 

 near the upper Rio Chalia, which beds form the very top of the Patago- 

 nian series. 



Terebmtnla macrostoma of Philippi (1887, p. 217, pi. 49, f. 3 and Moer- 

 icke, 1896, p. 587) from the Pliocene beds of Coquimbo and Caldera, 

 Chili, seems to be closely allied, but differs in the larger foramen and the 

 equally convex valves. Moericke regards this form as the ancestor of the 

 living Magellania venosa. The brachial apparatus of the Chilian fossil is 

 said to be that of a Magellania, but it is imperfectly known. Pilsbry 

 (1897), without knowing the brachial apparatus, has united our Cape Fair- 

 weather species with Magellania venosa, but since I succeeded afterward 

 in working out the brachial apparatus, we must separate it from this genus 

 altogether. 



Genus: BOUCHARDIA Davids. 

 21. BOUCHARDIA ZITTELI v. Ihering. 



PI. XIII, Fig. 9 .. 



1897 Boiich. zitt. v. Ihering, in: Rev. Mus. Paul, v. 2, p. 268, textfig. 6. 



Shell ovate, smooth. Beak short, triangular, nearly straight, foramen 



small and terminal; deltidium obsolete (fused with the shell); area slightly 



