3 ۱ APPENDIX. 331 
- CATALOGUE -—Continued. 
No. = Name. | Locality. 
32 | Littorina, (undetermined) : San Diego 
33 | Melampus, (undetermined) do 
34 | Oliva biplicata, Sowerby San Pedro 
35 | *Potamis pullatus, Gould < San Diego.... 
36 | “Amnicola protea, Gould Colorado Desert 
37 | *Amnicola longinqua, Gould do... 
38 | *Planorbis ammon, Gould. . - ۱ Colorado Desert — Ocoya Creek 
39 | *Physa humerosa, Gould Colorado Desert....... 
40 | Succinea, (undet Ocoya Creek 
41 | Helix Vancouverensis, Lea San Francisco 
42 | Helix San Diegoensis, Lea Point Reyes 
43 | Helix infumata, Gould | do 
44 | Helix Oregonensis, Lea | Cypress Point 
I.—FRESH-WATER SHELLS FROM THE COLORADO DESERT. 
PHYSA HUMEROSA, Gould. 
[ Proceed. Bost. Soc. Nat. Hist., V. 128. Feb. 1855.] 
T. notin, subrhomboidea, polita; spira acuta, anfractibus quinque tabulatis ; ; apertura 
3 ad 3 long; idtudinis teste adequans, posticd obtusa ; labro expanso, columella vix Pm 一 
Pl. XI, figures 1, 2, 3, 4, and 5. 
Shell rather "P and solid, subrhomboidal, polished ; all the specimens seen, (quite numerous, 
‚and apparently not weathered,) porcelain white. Whorls five, each with a broad, square 
shoulder, and forming an elevated, acute spire; aperture usually about two-thirds the length 
of the shell, sometimes but little-over one-half; posterior angle obtusely rounded ; outer lip 
slightly flaring, when viewed in profile it is slightly advanced posteriorly so as to form a recess 
at the junction ; ; pillar without any conspicuous fold, thickly covered with enamel, broadly 
rounded and expanded at the base. Umbilical region nearly perforate. 
‚Length of an ordinary specimen, half an inch ; breadth, three-eighths of an inch; length of ` 
a variety, seven-tenths of an inch. 
Found in the Colorado Desert, by W. P. Blake; also at ups River, by Dr. T. H. Webb. 
The broadly tabulated whorls, with the acute, elevated spire and foldless pillar, clearly dis- 
tinguish this species. P. tabulata, Gould, from New Zealand, is similar, as well as some 
varieties of P. ancillaria, Say, as figured by Haldeman, especially his figure 7, which he desig- 
nates as a monstrosity; but the spire is more elevated, and the deep suture always renders the 
whorls distinct, and the absence of a columellar fold is a still further distinctive mark, It 
would be difficult to distinguish the young by themselves from several other species, though they 
begin to show the angularity of the whorls quite early. 
PLANORBIS AMMON, Gould. 
[ Proceed. Bost. Soc. Nat. Hist., ۲۰129. Mar. 1855.] 
T. magna, discoidea, subconica, subtiliter striata ; latere sinistro late et profundé concavo, 
