ORTMANN : TERTIARY INVERTEBRATES. 89 



by v. Ihering becomes apparent (see fig. 4'): flat, radiating ribs, as broad 

 as the intervals and hardly higher than the latter. Since this destruction 

 of the outer layer of the shell takes place chiefly near the apex and on 

 the middle part of the surface (see fig. 4*), while the outer layer as a rule 

 is still preserved on the anterior and posterior ends, we often see the con- 

 dition described for C. alta: a number of ribs in the middle part of the 

 shell, which are apparently lacking on the anterior and posterior ends. 

 All our individuals from Santa Cruz show this condition of the partly 

 exfoliated surface, while those from Mt. of Observation are in a better 

 state in this respect (see fig. 4). 



Thus, of the characters given by v. Ihering, only that of the number of 

 sulci of the area deserves any attention, and it seems as has been shown 

 above that even this one does not warrant the establishment of two dif- 

 ferent species. If I am mistaken in this opinion, if there are really two 

 different but closely allied species at Santa Cruz, we possess only one of 

 them : C. dalli, but not what v. Ihering calls C. alta. The little uncer- 

 tainty that remains in this respect is chiefly due to the fact that the differ- 

 ences of sculpture of the surface mentioned by v. Ihering are not illustrated 

 by any good figures: that of C. nmlticostata, given in 1897 (pi- 5> ^ 2 9)> 

 is quite, insufficient. 



Record of specimens : Mouth of Santa Cruz River ; 4 double, 7 right, 

 3 left valves. (Some of them labelled 200' and 250' above high tide.) 

 Mt. of Observation, lower horizon ; 2 double, i right, 2 left valves. 



Distribution : Santa Cruz (Sow., v. Ih.); La Cueva and Jack Harvey 

 (v. Ih.); Port Desire (Sow.). Patagonia formation (v. Ih.), Oamaru and 

 Pareora systems (Oligocene and Miocene) of New Zealand (Hutton). 



Affinities: C. cliilensis Phil. (1887, p. 189, pi. 40, f. 2), from the Navidad 

 beds of Chili comes extremely near to this species, the only difference is 

 the less high and more elongated form. From the Oligocene and Miocene 

 beds of New Zealand Hutton has described three more species, which are 

 hardly distinguishable. 



Sowerby compared this species with C. dectissata Sow. (= crassatina 

 Lmck.), which is found in Eocene beds of Europe, and a similar form is 

 found in the Eocene of the eastern United States : C. gigantca Conr. (see : 

 Clark, 1896, pi. 30-33). Since species of this genus have not been found 

 in the northern hemisphere in younger Tertiary beds, we are confronted 

 here with a pronounced relation to Eocene : but the value of this case is 



