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PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 
counterbalanced by the fact that the identical species or very closely allied 
forms are found in beds that are considered Oligocene, Miocene and Plio- 
cene (Hutton, 1886, p. 365), in Chili and New Zealand, and further by 
the fact that the genus still exists in the recent seas. 
28. Cu cull ae a (Cucullaria) darwini (Philippi). 
PL XXV, Fig. 5* 6 . 
1887 Area darw. Philippi, Tert. Quart. Verstein. Chiles, p. 188, pi. 36, f. 3. 
1897 Cucullaria tridentata v. Ihering, in: Rev. Mus. Paul., v. 2, p. 237, 
pi. 4, f. 22, pi. 5, f. 28. 
1900 Cucullcea darwini Ortmann, in: Amer. Journ. Sci., v. 10, p. 379. 
Shell elongate-oval, subtrapeziform, with fine radial ribs, which are flat 
and separated by fine but sharp sulci. Toward the lower margin the ribs 
appear geminate or double, through the development of a slight sulcus in 
the middle of each rib. The ribs are crossed by distant, distinct lines of 
growth. Apices swollen, closely approaching each other. Anterior end 
of shell short, rounded; posterior broader, with rounded angles. Area 
very small. Teeth of hinge (according to v. Ihering): 2-3 horizontal 
anterior ones, and 3 posterior. Small vertical teeth below the apex. 
Our largest individual measures: length, 29 mm; height, 17 mm; but 
the species grows much larger, since v. Ihering gives : length, 42; height, 24. 
Remarks : According to v. Ihering this species belongs to the subgenus 
Cucullaria. My specimens agree completely with his figure in outline, • 
but they are smaller and do not show the hinge. 
There cannot be the slightest doubt that this species is the same as 
Philippi’s Area darwini. Philippi’s reconstruction of the anterior part of 
the shell is not quite correct (it being too high), and this is the only dif- 
ference from v. Ihering’s figures. The fact that Philippi’s species is from 
Santa Cruz is sufficient to establish this identity. 
Record of specimens : Mouth of Santa Cruz River, 1 double, 1 right 
valve ; Las Salinas, 2 right valves. 
Distribution : Santa Cruz (Phil.); Jegua quemada, Suprapatagonian beds 
(v. Ih.). 
Affinities : The type-species of the subgenus or genus Cucullaria is C. 
heterodonta Desh. from the Eocene of the Paris basin (see: Deshayes, 
