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If these shells had been examined independently of the other collections, they would probably have been considered, from the characters of the two Terebratulae, and from the Spirifer, as oolitic; but considering that the first species, and according to Professor Forbes, the four first, are identical with those from Coquimbo, the two formations no doubt are the same, and may, as I have said, be provisionally called cretaceo-oolitic.
On the other hand, the two Terebratulae and the Spirifer point, in the opinion both of M. d'Orbigny and Professor Forbes, to the oolitic series.
And there by the dim light that fell upon the desk, in the silence of that little retreat so high above the street, surrounded with objects what had come from distant corners of the earth and from the depths of the sea, when my mind wandered, and I became fatigued because of the mysterious differences in the forms of animals, and because of the infinite variety of shells, with what emotion I wrote down in my book, opposite the name of a Spirifer or a Terebratula, such enchanting words as these: "Eastern coast of Africa," "coast of Guinea," "Indian Ocean."
Professor Forbes adds, that, possibly, internal characters may exist, which would distinguish the American species from its European allies. Spirifer linguiferoides, E. Forbes. M. d'Orbigny considers it as perhaps indicating the Jurassic period. Ammonites, imperfect impression of.
Hence M. d'Orbigny, not having himself examined this country, has concluded that there are here two distinct formations; but the Spirifer and T. aenigma were certainly included in the same bed with the Pecten and Ostrea, whence I extracted them; and the geologist M. Domeyko sent home the two Terebratulae with the other-named shells, from the same locality, without specifying that they came from different beds.
I should like to present you with a memoir or monograph of mine, just published, on Spirifer and Orthis, but I will take good care to let no one pay postage on a work which, by its nature, can have but a very limited interest. . .I will await your arrival to give you these descriptions. I am expecting the numbers of your Fossil Fishes, which have not yet come. Humboldt often speaks of them to me.
In what sense is the living Waldheimia less embryonic, or more specialized, than the palæozoic Spirifer; or the existing Rhynchonellæ, Craniæ, Discinæ, Lingulæ, than the Silurian species of the same genera?
The Mollusca In what sense is the living Waldheimia less embryonic, or more specialised, than the palaeozoic Spirifer; or the existing Rhynchonelloe, Cranioe, Discinoe, Linguloe, than the Silurian species of the same genera?
The 'Mollusca'. In what sense is the living 'Waldheimia' less embryonic, or more specialized; than the paleozoic 'Spirifer'; or the existing 'Rhynchonellae', 'Craniae', 'Discinae', 'Lingulae', than the Silurian species of the same genera?
Terebratula aenigma, var. Spirifer Chilensis. Mingled together in alternating beds in the main valley of Copiapo near Las Amolanas, and likewise higher up the valley: Pecten Dufreynoyi. Turritella Andii. Terebratula aenigma, var. as at Guasco. Astarte Darwinii. Gryphaea Darwinii. Gryphaea nov. species? Perna Americana. Avicula, nov. species. Pecten Dufreynoyi. Gryphaea Darwinii?
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