9O PATAGONIAN EXPEDITIONS : PALEONTOLOGY. 



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. CUCULL^EA (CUCULLARIA) DARWINI (Philippi). 



PI. XXV, Fig. 5"- . 



1887 Area darw. Philippi, Tert. Quart. Verstein. Chiles, p. 188, pi. 36, f. 3. 

 1897 Cttcitllnria tridentata v. Ihering, in: Rev. Mus. Paul., v. 2, p. 237, 



pi. 4, f. 22, pi. 5, f. 28. 

 1900 Cttcullcea danvini 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, 1 7 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, i double, i 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 Ctictillaria is C. 

 heterodonta Desh. from the Eocene of the Paris basin (see: Deshayes, 



