conditions necessary for the deposition and present distribution of the sandstones, clays and conglomerates, together with the preservation of remains of the faunas characteristic of each.

Many have noticed and Prof. J. E. Todd has recorded the presence of great deposits of bones at various localities in the White River beds. He describes them as literally covering the ground in places where they have weathered out over areas frequently of more than an acre in extent. It is not only difficult, but I think impossible to account for these accumulations of bones of terrestrial animals at the bottom and in the very middle of a great lake. Since the surrounding clays are usually almost destitute. of bones, it is difficult to understand how the dead carcasses of so many animals were driven or drawn as by a magnet to so limited an area. Accepting the other theory, however, we have seen how during the rainy season the deer, tapirs and other animals are driven to the islands over the flood-plains of the great South American rivers. Since in exceptionally high freshets the lower of these islands become submerged it is not difficult to understand how great numbers of these animals must annually perish, and indeed it is a well-known fact that frequently great numbers of them are caught on low islands and, driven by the rising waters to more limited confines, they are finally all drowned when the island becomes entirely submerged. To such or similar conditions the great deposits of bones in the Oligocene and Miocene deposits of the West may owe their origin. I have frequently observed these deposits, though not covering so great an area as that recorded by Todd, and I have always without exception noted that in the Oligocene beds they occurred in the very fine clays, while in the upper or Miocene deposits they occur in the finer sandstones. Although bones are fairly abundant in the sandstones of all these series of beds, I never observed these extremely rich deposits in the coarse sandstones or conglomerates.

The above facts, together with those brought forward by Dr. Matthew, have driven me, contrary to my earlier opinion, to reject the theory of a great lake and accept that of small lakes, floodplains, river channels and higher grass-covered pampas as the conditions prevailing over this region in Oligocene and Miocene times.

CARNEGIE MUSEUM, March 31, 1902.

ON THE MOLLUSCAN FAUNA OF THE PATAGONIAN TERTIARY.

BY H. VON IHERING.

(Plate XIX.)

(Read April 3, 1902.)

During the last ten years the exploration of the Patagonian and Argentine Tertiary has been very actively prosecuted, but the results of the new studies have not always represented genuine progress.

The

This refers particularly to the deposits of Entre Rios, which Alessandri regarded as Eocene from his studies of Selachian teeth, while A. Smith Woodward, reëxamining the same material, came to the conclusion that this formation is Miocene or Pliocene. study of the Mollusca of the Entre Rios beds led me to the opinion that they are Miocene, while Borchert, in view of the large proportion of recent species in this fauna, refers the formation to the Pliocene.

Having at my disposal one of the best collections of marine shells from the Brazilian and Argentinian coasts, I have carefully examined Borchert's work. This author has had access to a much richer collection of Entre Rios mollusks than I myself, in which are represented well-preserved examples of some species-e. g., Cardium magnum Born-of which I have seen only casts. This circumstance does not, however, entirely explain the divergence of our opinions, which is rather due to a number of incorrect determinations by Borchert. The small shell which he believes to be Dione purpurata Lam. is not referable to that species. The opinion that the young shell differs in outline from that of the adult is refuted by the large series of specimens in my collection. It is not reasonable to attach much importance to such young shells, especially if represented only by a single specimen.

"Cryptogramma brasiliana Gm." is not this species at all, but a different and extinct species, characterized by its numerous coarse concentric ribs, as also by numerous radiating striæ. Beside these two species, the following are certainly erroneously determined:

Lithodomus patagonicus d'Orb.

Modiola tulipa Lam.

Nucula puelchana d'Orb.

Tivela argentina Sowb.

Solecurtus platensis d'Orb.

Marginella prunum Gm.

Columbella acuta Stearns.

Of the nineteen species which the author regards as still existing at least nine are incorrectly determined. Admitting that the remaining ten species are accurately determined, the proportion of living species in the Paraná formation is as 10: 60, or 17 per cent.

Borchert's attempt to prove that the Paraná formation is Pliocene must be regarded as a failure; it is opposed to the opinion of d'Orbigny, Philippi and von Ihering, all of whom were well acquainted with South American marine Mollusca, both recent and fossil. We must continue to regard the Paraná formation as Miocene, while the Pliocene of Argentina is represented in the south by the Cape Fairweather beds, and in the north by the Tehuelche formation. Of the latter the new collection of Carlos Ameghino contains an instructive representation, with many new species of Pectinida, Carditida and Venerida.

From the marine deposits in the upper part of the Pampean formation I have a relatively large collection. As the species are all still living, I am obliged at present to consider the "Pampeano superior" of Ameghino as Pleistocene. It is interesting to observe that in this formation are two different horizons, the older of which contains Ostrea arborea Ch., Purpura hæmastoma L., and other species now common on the Brazilian coast, but which are wanting in the later horizon, where they are replaced by Ostrea puelchana d'Orb. and other Patagonian species.

With regard to the Patagonian formation, many new forms are contained in a large collection sent to me this year by Dr. Florentino Ameghino, and gathered by his brother Carlos in the years 1899 and 1900. This great collection contains representatives of three different faunas, but the greater part of it comes from the Patagonian formation. As I have studied many important collections from this formation, and as my friend Dr. A. E. Ortmann has also discovered many new forms in the collections of the Princeton Expedition, it was very surprising to find a great number of new and interesting forms in this new collection. I reserve the description of these new species until Dr Ortmann's report has been published, and describe here only two of the most striking new species.

NAUTILUS CAROLI-AMEGHINOI, sp. nov.

(Plate XIX, Figs. 1, 2.)

Nautilus testa suborbiculari, imperforata, lævi, suturis simplicibus, siphone interno, in fundo fossæ latæ situ.

The shell, which is filled with matrix and not very well preserved, is of suborbicular shape, subcompressed and much enlarged toward the aperture. The outer or peripheral part of the shell is rounded, smooth and with simple sutures. There is no umbilicus, but a pit at the central point of origin of the outer lip of the body-chamber. In this groove, the wall of which covers the umbilicus, there is, opposite to the origin of the outer lip, a crista, the prolongation of which passes into the dorsal wall of the body-chamber. The siphon is placed at the bottom of a large and deep hollow, which has an internal situation-that is to say, nearer to the dorsal than to the ventral or external margin of the septum.

I take great pleasure in dedicating this new species, which is the first representative of the class Cephalopoda from the Tertiary of Patagonia, to Mr. Carlos Ameghino, whose excellent work in the geological exploration of Patagonia I appreciate very highly. Locality: Golfo de San Jorge, Cabo Tres Puntas. Formation: "Patagonico medio."

NEOINOCERAMUS AMEGHINOI, gen. et sp. nov.

(Plate XIX, Figs. 3, 4.)

Testa solida, compressa, oblique-ovata, antice posticeque paullulum hiante, concentrice laminato-costata, laminis altis subreflexis distantibus, interstitiis lævibus; auriculis anticis magnis, posticis minoribus; area ligamentale lata brevi.

The shell is large, solid, very obliquely ovate, slightly compressed and gaping on both sides. The anterior lateral margin is convex, passing gradually into the arched ventral margin; the posterior