NO. 1250. FOSSIL SHELLS OF THE COLORADO DESERT— STEARyS. 299 
Plate XXII. 
Recognized species of PJiysa. 
The figures on this plate are taken from Binney's Land and Fresh Water Shells 
of North America, Part II, Smithsonian Institution Miscellaneous Collections No. 143, 
Washington, September, 1865. The numbers in parentheses and the page num- 
bers correspond with those in the above publication. 
Fig. 1 (127). Phimilordi Baird (p. 76). 
2 (128). Fhysa gabbi Tryon (p. 77). 
3 (129). Physa gabbi Try on (p. 77). 
4 (130). Physa gyrina Say (p. 77). 
5 (133). Physa ampuUacea Gould (p. 79). 
6 (134). Physa ampuUacea Gould (p. 79). 
7 (135). Physa ampuUacea Gould (p. 79). 
8 (139). Physa ancUlaria Say (p. 81). 
9 (140). Physa obesa l)e Kay (p. 82). 
10 (142). Physa oscidaiis Haldeman (p. 83). 
11 (143), Physa mexicana Philippi (p. 83). 
12 (144). Physa heterostropha Say (p. 84). 
13 (146). Physa osculans Haldeman (p. 85). 
14 (156). Physa virginea Gould (p. 92). 
15 (157). Physa humerosa Gould (p. 92). 
16 (158). Physa virgata Gould (p. 93). 
17 (168). P/)_(/.<(o ?7i/fns Philippi (p. 98). 
Plate XXIII. 
Variations of desert Physidse. 
Figs. 1, 2, 3, 5, 10, 17. P. humerosa and ordinary varieties. 
7. P. Jiumerosa, extreme variation. 
29. P. humerosa, typical; compare with Binney's fig. 157. 
14, 16, 17. P. humerosa, unusually large. 
44, 46, 50, 52. Compare with P. ampnUacea, Binney's 133. 
53, 55, 56. P. virginea; compare with Binney's 156 and same author's 129, P. gabbi. 
24. P. mexicana; compare witli Binney's 139, P. anriUaria. 
6, 8, 9. P. humerosa, abnormal, very short apex, etc. 
24, 26. P. mexicana, nearly or quite typical; see Binney's 143. 
13, 18, 22, 23. P. mexicana, ordinary varieties. 
8, 27. Hybrids of humerosa and mexicana, or varieties of either. 
54. P. heterostropha, robust form, approaching ampidlacea. 
Plate XXIY. 
Variations of desert Physidse. 
The figures in this plate, illustrating diversity of form, were drawn by the author 
from specimens collected by Prof. George Davidson ^ at or near Indio in 1883, and 
referred to on page 290 as a "first series." The shells are now unfortunately mis- 
placed or destroyed; but the drawings were made soon after they were received. 
Fig. 1 is very near to fig. 7 in Plate XXIII and represents an extreme variation from 
P. humerosa. 
3 is unique in being the only specimen of this form or shape. 
4 may be compared with fig. 33 of Plate XXIII, showing a triple repetition of 
the anterior part of tlie aperture. 
5-10. Varieties of P. Jiumerosa- or P. mexicana, or hybrids of the two species. 
11. Another rare variety; should be compared with P. osculans, Binney's 142. 
12, 13, 13a, 14, 14a, 14b. Varieties of P. heterostropha from sweet water. 
^ American NaturaUst, October, 1883, p. 1014 et seq. 
