Explanation of Plates VIII, IX, X. 



Note: The microphotographs of periostracal sculpture reproduced in the 

 accompanying plates were made by Mr. John Howard Paine. The remaining 

 specimen photographs were made by Messrs. John Howard Paine and Berton 

 W. Crandall. The illustrations on Plate VIII, and fig. 1 of Plate IX, are from 

 field photographs taken by the author. 



Plate VIII. — Fig. 1. — Lower Whitewater Canyon, San Bernardino Mountains, 

 California, looking north. Stations I and III of the present paper are at 

 the base of the canyon wall in the distance at the left. The two palms in 

 the foreground are probably the westernmost endemic specimens of Neo- 

 washingtonia filamentosa Sudw. Photograph taken April 1, 1920. 



Fig. 2. — South slope of small side canyon tributary to Whitewater Canyon, 

 San Bernardino Mountains, California. Station II, the type locality of 

 Micrarionta aquae-albae, is under the small tree to the right of the center 

 of the picture. Photograph taken April 1, 1920. 



Fig. 3. — Looking down Little Palm Canyon, Riverside County, California, 

 from a point on the east wall above the junction with the main canyon; 

 a characteristic habitat of the snail, Micrarionta wolcottiana. Stations 

 XI and XIII are near the center of the picture. The desert slopes of the 

 San Jacinto Range above Palm Springs loom in the background. Photo- 

 graph taken April 3, 1920. 



Plate IX. — Fig. 1. — Looking up the main fork of Palm Canyon, Riverside 

 County, California, from a point near its junction with Little Palm Creek. 

 The abundant palms are Neowashingtonia filamentosa Sudw. Stations X 

 and XII are visible in the nearer distance. Photograph taken April 3, 



,. 192 °- 

 Figs. 2-4. — Micrarionta aquae-albae n. sp. Three views of the type specimen, 



from Station II, Whitewater Canyon, California; x 4. 



Fig. 5. — Micrarionta aquae-albae n. sp. Upper surface of part of body 

 whorl of type specimen a little back of the aperture, greatly magnified 

 to show the periostracal sculpture; enlarged about 18 diameters. 



Fig. 6. — Micrarionta aquae-albae n. sp. Greatly magnified view of apical 

 whorls of specimen from Station I, Whitewater Canyon, California, 

 showing the periostracal sculpture; enlarged about 18 diameters. 

 Plate X. — Figs. 1-3. — Micrarionta xerophila n. sp. Three views of type speci- 

 men from Station VII, west of Indian Well, California; x 2. 



Fig. 4. — Micrarionta xerophila n. sp. Greatly magnified view of apical 

 whorls of type specimen, showing the periostracal sculpture; enlarged 

 about 19 diameters. 



Figs. 5-7. — Micrarionta harperi Bryant. Three views of specimen collected 

 by Bryant at Warner's Hot Springs, California; Cal. Ac. Sci. 8676A; x 2. 



Fig. 8. — Micrarionta harperi Bryant. Greatly magnified view of apical 

 whorls of same specimen, showing the periostracal sculpture. 



