GEOLOGY. 
161 
Purpura labiosa, Gray ; recent at Valparaiso.* 
Monoceros crassilabrum, Lam. ; recent at Valparaiso, &c. 
Monoceros crassilabrum var. ; recent at Valparaiso, &c. 
Concholepas Peruviana, Lam. ; recent on the whole line of the Pacific side of the 
South American coast. Two specimens, each with balani attached, the young of B. 
psittacus. 
With respect to the strata designated as marl and sand-stone, the collection made 
by Lieutenant Belcher affords no evidence that is decisive of their age and character. 
The marl and sand-stone seem to be tertiary, and the imperfect coal included in them 
a tertiary lignite ; the petrified wood perforated by the teredo has more the appearance 
of fossil wood from the London clay than from any secondary stratum. The ammonite 
mentioned by Lieutenant Belcher is the only fossil indicative of strata of secondary 
formation. It is much to be regretted that two vertebrae found with this ammonite, 
and also a vertebra six inches in diameter found near Point Parra, have been mislaid. 
It is probable that great part of the extensive deposits coloured as alluvial, parti- 
cularly those at a distance from any existing rivers, on the summits of hills, and on ele- 
vated table lands, are either tertiary or diluvial; but no observations were made 
sufficiently minute to establish any certain conclusions upon this point. — Ed. 
EXTRACT FROM THE NOTES OF MR. COLLIE. 
The form of the Bay of Concepcion is oblong, about eight miles by six, extending 
in its longest axis nearly north and south (see map, pi. II. Geology). The land rises 
from the sea, towards the entrance, in perpendicular and high cliffs, which gradually 
diminish towards the head of the bay, where a long and low sandy beach is backed by 
low marshes and meadows. Near the entrance of the bay, the Island of Quiriquina 
rises in bold and frequently inaccessible pi’ecipices, and is nearly connected by a sub- 
aqueous reef with the northern extremity of the peninsula that forms the western shore 
of the Bay of Concepcion, and separates it from the sea. At the extremity of this 
peninsula is a bed of green-stone. 
The Island of Quiriquina exhibits clay-slate near its north-eastern extremity, but 
its main body is composed of sand-stone and alluvial deposits. On its southern end we 
find loosely aggregated sand, and large and small rolled stones, united more or less 
firmly by calcareous cement. The small stones are chiefly slate, green-stone, quartz, 
and lime stone. A calcareous marl forms the lower part of the east cliff of this island 
in several places. In some parts, also, beds of broken and petrified shells compose the 
beach. A great part of the western shore of the island is so perpendicular that, having 
once got on the top of the high land, it is impossible to descend and examine the base. 
* There are in the collection some other specimens of a Purpura also found recent at Valparaiso, and considered 
by some to be Purpura labiosa in an advanced stage of growth. The difference, however, is so striking as to war- 
rant the inquiry, whether these specimens are not undescribed, and specifically distinct from Purpura labiosa. 
