direction of the broad peduncle. Cusp inflected and carrying twentythree slender denticles.

FIG. 2.-Lingual dentition of Amnicola dalli, Call x 400.-Beecher.

a.-Two of the transverse rows of the odontophore, showing the normal position of the teeth. The teeth are considered as opaque. Analysis. b.-Outer laterals. c.-First laterals. d.-Intermediate teeth. .-Rachidian teeth.

FIG. 3.-Intermediate teeth (×400) showing mode of articulation.-Beecher.

"Outer lateral tooth hamate, with no marked distinction between the body and peduncle. Free extremity incurved and bearing thirty-four minute denticles. The denticle formula is, therefore

"The apparent articulation of the intermediate teeth, as described above, was observed in a fragment of an odontophore which presented a lateral aspect under the microscope. It is not known that this feature has ever been noted in any other species, although it very proba

bly occurs in many which have foraminated or bullate teeth. This disposition of the teeth would allow great flexion of the odontophore without their displacement."

This quite distinct form was collected in considerable numbers at Symon's Stage Station, near the foot of Pyramid Lake, Nevada. Its nearest congener is A. porata Say, from which it differs in elevation, sculpturing, and dentition. Since this last character is the one of chief importance, the description of the dentition is here given. Comparing the denticle formulæ of the two forms, thus:

the dissimilarity is strongly marked. Specimens may be seen in numerous private collections and in the cabinets of the Smithsonian Institution and the New York State Museum of Natural History.

LIMNEIDE.

Genus RADIX Montfort.

Radix ampla, var. utahensis, var. nov.
(Plate VI, Figs. 7-9.)

Testa globosa, sub-umbilicata, irregulariter costata, corneo-albida, sub-pellucida; spira parvula, conica; anfr. 4-44, convexi, supra valdeplani, rapide accrescentes, ultimo inflato, cum transversis costatis perspicatis minutissime corrugatisque; sutura sub-profunda, regulariter impressa; apertura elongato-ovata, effusa, intus margarita-alba; labrum simplex, marginibus callo junctis; columella reflexiuscula, antice recta.

Long. 13.40mm; lat. 7.10mm

Aper. long. 9.00mm; aper. lat. 5.90mm

Habitat, Lake Utah, Lehi, Utah.

Shell globose, somewhat umbilicated, irregularly costate, light horn color, nearly pellucid; spire rather small, conical; whorls four to four and one-half, convex, somewhat flattened above, giving rather a shouldered appearance to the whorls, rapidly increasing in size, the last whorl being inflated, with numerous rather marked transverse costæ, minutely wrinkled; suture somewhat deep, regularly impressed; aperture elongately ovate, effuse, approaching patulous, pearly white within; outer lip simple, the margin connected by a slight calcareous deposit; columella somewhat twisted, but straight in front. Dentition 22After Stimpson, Smithsonian Misc. Coll. No. 201, p. 14, Fig. 6; also ibid., No. 144, p. 80, Fig. 158.

unpublished. Length of largest specimen 16.82mm; breadth 8.88mm. The average of nine specimens gave a length of 13.40mm, breadth 7.10mm, with about the same ratio for corresponding measurements of aperture. Utah Lake, near Lehi, Utah.

This is a rare form in Utah Lake, its only locality so far as known. Its nearest affinity is indicated in the nomenclature adopted. In the preceding chapters its relation to Polyrhytis kingii Meek, has been noted. It was associated with abundant specimens of the Valvata herein described, and with Fluminicola fusca Hald., and Sphærium dentatum Hald. Specimens may be seen as above.

Genus LYMNOPHYSA Fitzinger.

Limnophysa bonnevillensis, sp. nov.

(Plate VI, Figs 10-13.)

Testa umbilicata, elongata, ventricosa vel bullata, solidula, obsolete striata, minutissime reticulata, in anfr. infra suturam ultimo longitudinaliter obsolete costulato; spira elevata, acuta; sutura perimpressa; anfr. 4-44, per-convexi, ultimo longitudinis testæ adæquante et subito accresente, ventricosa, basi subexpanso; columella subplicata, leviter callosa, regulariter arcuata; columella peristomateque continuatis; peristoma simplex, marginibus callo crasso junctis; apertura late-ovalis, totius longitudinis æquans, satis obliqua, postice angulosa. Species fossilis, Bonneville Lake beds, Utah. Quaternary.

Shell umbilicated, elongate, ventricose or bullate, somewhat solid, faintly striate and very minutely reticulated, below the suture the last whorl bearing faint longitudinal ridges or costa; spire elevated, acute; suture deeply impressed; whorls 4 to 42, very much rounded, sometimes tending to geniculation above, the last whorl equal to three fourths the whole length of the shell, rapidly increasing in size, much swollen, somewhat expanded at base; columella somewhat plicate, slightly callous, regularly arcuate; columella and peristome continuous; peristome simple, margins joined by a heavy callous which is continuous and so reflexed as to partially close the umbilicus; aperture broadly ovate, often patulous, equal to one-half the entire length of the shell, oblique, angled slightly behind.

Fossil, Quaternary. Bonneville Lake beds, Kelton, Utah.

The four largest specimens of the many in the collections give the following dimensions:

This shell resembles depauperate examples of L. sumassi, Baird (var. P. palustris Müller), but differs in not presenting a decussate surface, and in the columella being less strongly plicate. The greater number of specimens are somewhat malleated, though occasionally quite smooth specimens occur which approach nearest to L. desidiosa Say. Many present a patulous aperture, in which respect they resemble specimens of the genus Radix rather than true Limnophysa. The general outline of the specimens is that of L. adelina Tryon. Collected abundantly by Mr. G. K. Gilbert, in Upper Bonneville beds, at Kelton, Utah.

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Bull. 11- -4