ORTMANN : TERTIARY INVERTEBRATES. 
89 
by v. Ihering becomes apparent (see fig. zp): fiat, 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. zg), 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. zp). 
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. multicostata , given in 1897 (pi- 5, f. 29), 
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, 1 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. chilensis 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. decussata 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. gigantea 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 
