PALAEONTOLOGY OF THE SURVEY. 193 



PACHYDESMA, OmTod. 



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. 



OSTEEA, 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, PI. 2, fig. 4. — Ovate, thick, lower valve with a few lateral distant radi- 

 ating plicffi ; upper valve thick, concentrically undulated and rugose ; hinge area wide and 

 carinated on the margins. 



Localities. — Panza and Estrella valleys. 



Height, 2|- inches. The hinge of this shell resembles that of the preceding ; and, jjossibly, 

 it may be the old shell of that species, the specimens of which, in the collection, are evidently 

 all young shells. At Gaviote pass specimens of 0. panzana occur twice the size of those from 

 the above localities. 



DOSINLA., Scopoli. AZTHEMIS, Poli. 



DosiNiA ALTA, PI. — ., fig. — . — Obtuscly 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.) 



DosiNLi LONGULA, PI. 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 



