as we now find them. Presumably they represent climatic conditions not greatly removed from those of modern times, but they nevertheless occur at stations which are now absolutely destitute of the conditions essential to their growth. It is to shells of such occurrence that the above-quoted terms are applied.

The second special factor of the lacustrine history is embodied in the tufa deposits of the Lahontan area. These have been critically studied by Mr. Russell, who recognizes three varieties superimposed in the man

ner indicated by the diagram. The extreme height attained by the Lahontan waters during their first rise was 500 feet above the level of Pyramid Lake. Up to this height are found deposits of "lithoid" tufa. Over the "lithoid" tufa is deposited a distinct variety named "thinolite," but this reaches only one hundred feet above the surface of Pyra mid Lake. It rests unconformably upon eroded surfaces of the lithoid tufa, and is chronologically separated from it by an epoch during which the water fell to a lower plane than that marked by Pyramid Lake. The thinolite tufa therefore belongs to the second Lahontan epoch and is synchronous with a portion of the Upper Lahontan beds. After its formation the water rose to its highest level, 530 feet above Pyramid Lake, or 30 feet higher than the first great rise. During this second high stage a third variety of tufa was deposited, the "dendritic," but it failed to attain the height of the lithoid. Its upper limit is 320 feet above Pyramid Lake. Up to the 100-foot contour it rests upon the thinolite tufa. Higher up it is found in contact with lithoid tufa. Lake Lahontan had no outlet; and it is assumed that the salinity of its water varied with expansion and contraction just as that of Great Salt Lake is now known to vary. During the lithoid and dendritic epochs it was presumably a weaker solution than during the thinolite.

The reader who cares to inform himself more fully in regard to the history of these Quaternary lakes can do so by consulting the following literature:

U. S. Geographical Surveys West of the 100th Meridian. Vol. III.

Geology. Part I. Report upon the Geology of portions of Nevada, Utah, California, and Arizona, examined in the years 1871 and 1872. By G. K. Gilbert. Pp. 88-104.-Part III. Geology of portions of Utah, Nevada, Arizona, and New Mexico, explored and surveyed in 1872 and 1873. By E. E. Howell. Pp. 249-251.

U. S. Geological Exploration of the Fortieth Parallel. Vol. I. Systematic Geology. By Clarence King. Pp. 488-525.

U. S. Geological Survey. Second Annual Report. Contributions to the History of Lake Bonneville. By G. K. Gilbert. Pp. 169-200.

U. S. Geological Survey. Third Annual Report. Sketch of the Geological History of Lake Lahontan; a Quaternary lake of northwestern Nevada. By Israel C. Russell. Pp. 189-235.

U. S. Geological Survey. Fourth Annual Report. A Geological Reconnaissance in Southern Oregon. By Israel C. Russell. Pp. 435-462.

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ON THE QUATERNARY AND RECENT MOLLUSCA OF THE GREAT BASIN, WITH DESCRIPTIONS OF NEW FORMS.

BY R. ELLSWORTH CALL.

CHAPTER 1.

SYSTEMATIC CATALOGUE OF QUATERNARY AND RECENT SHELLS OF THE GREAT BASIN.

'The material herein reported upon was derived in part from collections made by the Great Basin Division of the United States Geolog ical Survey and in part from personal collections made under the auspices of the same organization. The material comes from numerous and widely separated localities, and is fairly representative of all the beds of ancient Lakes Lahontan and Bonneville. The first-named area furnishes the greater body of material, and also exhibits the more diverse fauna.

The later beds present three identical forms in common-Fluminicola fusca Hald., Helisoma trivolvis Say, and Limnophysa palustris Müllerno one of which is characteristic of either area. These identical forms represent two distinct families of gasteropods, the first named belonging to the Rissoida, the others to the Limnaida. Each of these great 'amilies is represented by the characteristic species of each series of lacustrine beds, the Limnæida being alone characteristically represented in the Lahontan beds, and the Rissoida alone characteristically represented in the Bonneville beds.

The field treated in this paper is entirely new, and the methods adopted are also new. The results have been put into the form of tables of measurements, and these tables have been used as the basis of graphic representation.

The facies of the shells studied in a measure correspond with differences in size. That is to say, the weight, sculpture, and other taxonomic features were found to vary in almost or quite as marked a degree as the size.

The material upon which the included discussion is based is exhibited in the following catalogue1:

LAMELLIBRANCHIATA.

UNIONIDE.

Genus MARGARITANA.

Margaritana margaritifera Linn.

This species is circumpolar. It appears over a considerable area of the northeastern United States, Nova Scotia, New Brunswick, Newfoundland, and Quebec. Its western limit in this area is Central Pennsylvania. It reappears in the headwaters of the Missouri River, and thence over all of the western United States, south to Arizona and north to British Columbia. It is somewhat common in streams near Salt Lake City, Utah, and occurs rarely at Elko, Nev., in the Humboldt River. It is far smaller throughout its western range than are its eastern congeners. It has been found fossil at one locality only in the Lahontan area, in the Walker River Cañon, Nevada. Within the Bonneville area it is semi-fossil, or post-Bonneville, at numerous localities and notably in Sevier Desert.

Genus ANODONTA.

Anodonta nuttalliana Lea. Observations on Unio, Vol. II, 77 (1838). Transactions Am. Phil. Soc., Vol. VI, Pl. 20, Fig. 62 (1838).

Anodonta wahlametensis Lea. Trans. Am. Phil. Soc., Vol. VI, Pl. 20, Fig. 64 (1838). Obs. on Unio, Vol. II, 78 (1838).

Anodonta oregonensis Lea. Trans. Am. Phil. Soc., Vol. VI, Pl. 21, Fig. 67 (1883). Anodonta californiensis Lea.Trans. Am. Phil. Soc., Vol. X, Pl. 25, Fig. 47. Obs. on Unio, Vol. V, 42 (1852).

Vide also, Stearns, "On the History and Distribution of the Fresh Water Mussels and the Identity of certain alleged species." Proc. Cal. Acad. Sci., Nov. 20, (1882), p. 4 et seq. In this paper a vast array of facts is brought out, together with the necessary data to render the synonymy as here given absolutely certain.

The synonymy here indicated is based upon extensive suites from various localities on the Pacific slope and in the Great Basin. In its various forms the species has a wide distribution through California, Idaho, Oregon, Washington Territory, British Columbia, Vancouver's Island, Nevada, and Utah. Specimens were dredged in Utah Lake 1. August 1883. In the Lahontan area it is especially abundant in the Humboldt River, and found sparingly in the Truckee River, Nevada.

The bibliographic references given in connection with this catalogue are such only as are easily accessible; no attempt has been made to furnish a complete bibliography.

The special use of this term is explained on page 10, ante,

It is found fossil in middle Lahontan beds at Mill City, Nev., and postLahontan beds on the desert east of Carson Lake. In the Bonneville area it has not yet been discovered in Bonneville beds, but abundant post-Bonneville fossils occur on Sevier Desert. It is somewhat common in fresh-water streams near Salt Lake City.

Sphærium striatinum Lam.

Cyclas striatina Lam.

CORBICULIDÆ.

Genus SPHÆRIUM.

Animaux sans Vertèbres, Vol. V, p. 560, (1818).

Sphærium striatinum Lam. Smithsonian Misc. Coll. No. 145, p. 37, Fig. 29 (1865).

Widely distributed in the United States and Canada. Found fossil only at Rye Patch, Nev., in Upper Lahontan beds.

Sphærium dentatum Hald.

Cyclas dentatum Hald (Prime), Smithsonian Misc. Coll. No. 145, p. 40, Fig. 32 (1865).

This species was originally described from Oregon, and has a somewhat limited distribution. In the Lahontan area it occurs in Humboldt River, at Elko, and fossil in Upper Lahontan beds at Rye Patch, Nevada. It is a very abundant species in Utah Lake, where it attains a great size. Found as a post Bonneville semi-fossil in great abundance upon the surface of Sevier Desert; occurs also in dredgings from Great Salt Lake, near the mouth of the Jordan River, whence it was doubtless drifted or floated.

Genus PISIDIUM.

Pisidium ultramontanum Prime. Smithsonian Misc. Coll. No. 145, p. 75, Fig. 85 (Appendix) (1865).

This species is rare and restricted in distribution. The original specimens came from California and Oregon. Found semi-fossil near Button's Ranch, Christmas Lakes, Oregon. As a fossil it occurs (a) in estuary of highest Lahontan two miles southeast of Brown's, Nev.; (b) section on west side of Truckee River, below Reservation Bridge; and (c) in Upper Lahontan beds at Rye Patch, Nevada.

Pisidium compressum Prime. Proc. Bost. Soc. Nat. Hist., Vol. IV, 164 (1851). Smithsonian Misc. Coll. No. 145, p. 64, Fig. 67 (1865).

This species is very widely distributed, ranging from New England to California, and north into Canada. It is everywhere rare. In Lahontan beds it has been found at the base of the bone-beds on the south side of Walker River Cañon, Nevada, below the Narrows. It is there Lower Lahontan. Three specimens, living, were dredged in August, 1883, in Utah Lake.