greater scale, near San Pedro on the river Parana, where he found widely
extended beds and hillocks of sand, with vast numbers of the Azara labiata,
at the height of nearly 100 feet (English) above the surface of that river.
(Ibid page 43.) The Azara inhabits brackish water, and is not known to be
found nearer to San Pedro than Buenos Ayres, distant above a hundred miles
in a straight line. Nearer Buenos Ayres, on the road from that place to San
Isidro, there are extensive beds, as I am informed by Sir Woodbine Parish,
of the Azara labiata, lying at about forty feet above the level of the
river, and distant between two and three miles from it. ("Buenos Ayres"
etc. by Sir Woodbine Parish page 168.) These shells are always found on the
highest banks in the district: they are embedded in a stratified earthy
mass, precisely like that of the great Pampean deposit hereafter to be
described. In one collection of these shells, there were some valves of the
Venus sinuosa, Lam., the same species found with the Mactra on the banks of
the Uruguay. South of Buenos Ayres, near Ensenada, there are other beds of
the Azara, some of which seem to have been embedded in yellowish,
calcareous, semi-crystalline matter; and Sir W. Parish has given me from
the banks of the Arroyo del Tristan, situated in this same neighbourhood,
at the distance of about a league from the Plata, a specimen of a pale-
reddish, calcereo-argillaceous stone (precisely like parts of the Pampean
deposit the importance of which fact will be referred to in a succeeding
chapter), abounding with shells of an Azara, much worn, but which in
general form and appearance closely resemble, and are probably identical
with, the A. labiata. Besides these shells, cellular, highly crystalline
rock, formed of the casts of small bivalves, is found near Ensenada; and
likewise beds of sea-shells, which from their appearance appear to have
lain on the surface. Sir W. Parish has given me some of these shells, and
M. d'Orbigny pronounces them to be:--

1. Buccinanops globulosum, d'Orbigny.