el Sas 
seinen aia 
1a 
——— 
Mineralogy and Geology. 271 
the Pecten, occurring even in the northern regions between Mostan 
and Guancavelica in such incredible numbers, that it forms fields, nay, 
mountains of petrifactions, long and very generally known to the na- 
tives under the name of * Choro, ampas.” ( Pecten alatus, Dufresnoyi, 
@’Orb.) It was this shell also that, in 1761, excited so great astonish- 
ment in Ulloa at the em blaeution above the level of the sea, at 
107, t. 22) occurs with the pecten-strata, it is evident that all these 
beds in Peru, as at Coquimbo and Copiapo, must be conjoined at least 
with the gault; a result which is most strikingly channel by an 
h M. Domeyko has sent to Paris. This is i per- 
already described and figured by Morton, andthe position of which 
above the gault at Friederichsberg has been very. nip a ascertained 
by — Romer. 
others, some perfectly chutadaviitie neocomie n shells :— ~ 
<ed Emerici, (D’Orb., p. 216,) conoidea, paar ; Holaster dila-— 4 
tatus and. Holaster complanatus or Spit s retusus, both identified 7 
by Agassiz; Diadema Bourgeti, also’ Méletedined as such in Neufcha- 
tel; Pecten cretosus, Brgnt. and Pecten" quinquecostatus. & 
According to this, the cretaceous formation in South Misetica ap- . . 
pears to be developed in an entirely different’ manner, in much greater ¥ ie 
thickness and variety than to the north of the Gulf of Mexico, and the 
agreement with the European cretaceous strata is also much more. | 
id 
complete in the Andes, It is, ae sel vip a thal ‘in 
North America the cretaceous strata are spread out quite heneoptally ‘ 
over e spaces, and that they seni chiefly of clay an "aes 
yecoherent masses. In South America we onl 
’ 
often believes them to be pure quartz, as ‘between the Maranon and, ~ 
Lima ; along with this, the strata are never horizontal, but always more *. 
or less inclin ed; a-disturbed position which they evidently can only .+ é 
Uwe to powerful ‘disturbing forees. ‘There can be less doubt in regard 2: 
to this, when it is seen, as “Meyen informs us, hi the fone lege vrnid 4 
of the Volcano: of Maypo consists for tw: sn of its hos. ad bal * 
a 
