PALAEONTOLOGY OF THE SURVEY. 
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PACHYDESMA, Conrad. 
Pachydesma inezana, PI. 5, figs. 2 and 4.—Triangular, equilateral, convex; anterior and 
posterior margins equally oblique ; anterior extremity rounded; posterior extremity acutely 
rounded ; posterior side sub-cuneiform ; cardinal and lateral teeth robust. 
Locality. —Santa Inez mountains, Santa Barbara county, California. 
This species is smaller than P. crassatilloides, Con.; proportionally shorter, with straighter 
lateral outlines, more robust teeth, and a broader cardinal plate. It is the first fossil species of 
the genus that I have seen. The only recent species inhabits the coast of California. Length, 
3 inches. 
CRASSATELLA, Lam. 
Crassatella collina, PI. 6, figs. 1 and 2.—Triangular, inequilateral, ventricose, thick ; 
anterior and posterior margins very oblique, and nearly equal in slope—the anterior a little 
incurved, the posterior straight or a little sinuous; umbo contracted or laterally compressed and 
triangular; summit prominent; posterior side cuneiform. 
Locality. —Santa Inez mountains. 
A fragment of one valve, the lower portion wanting. Length, If inch. 
OSTREA, Lin. 
Ostrea subjecta, PI. 2, fig. 3.— Very irregular, valves sometimes subplicated ; cardinal 
area broad and carinated laterally ; cartilage pit but slightly impressed. 
Locality. —Between Santa Clara river and Los Angeles valley, on the Sierra Monica. 
Height, 2 inches. (In plate 2, this fossil is improperly included under the 0. Panzana.) 
Ostrea panzana, PL 2, fig. 4. —Ovate, thick, lower valve with a few lateral distant radi¬ 
ating plicm ; upper valve thick, concentrically undulated and rugose ; hinge area wide and 
carinated on the margins. 
Localities. —Panza and Estrella valleys. 
Height, 2f inches. The hinge of this shell resembles that of the preceding ; and, possibly, 
it may be the old shell of that species, the specimens of which, in the collection, are evidently 
all young shells. At Graviote pass specimens-of 0. panzana occur twice the size of those from 
the above localities. 
DOSINIA, Scopoli. AZTHEMIS, Poll 
Dosinia alta, PL—., fig.—.—Obtusely subovate or suboval, slightly ventricose; elevated; 
posterior margin curved, profoundly oblique; base irregularly and profoundly rounded ; 
summits prominent, acute; surface marked with numerous fine concentric impressed lines ? 
beaks medial. 
Locality. —Salinas river, Monterey county, California. 
There is but only one cast in the collection ; portions of the shell remaining appear to have 
concentric sulci. It is quite an elevated species, occurring 4 inches in height at Hill’s ranch, 
Salinas river. (The illustration of this specimen has been accidentally omitted.) 
Dosinia longula, Pl. 7, fig. 2. — Shell regularly ventricose, inequilateral, longitudinally 
oval, margins and base regularly rounded ; summit prominent; anterior margin more obtusely 
rounded than the posterior. 
Locality. —Occurs with the preceding. 
25 U 
