192 
PALAEONTOLOGY OF THE SURVEY. 
TAPES? MiiJdf. 
Tapes Montana, PL 5, figs. 3 and 5.—Suboval, ventricose, very inequilateral; posterior margin 
very oblique and rounded, end obtusely rounded ; basal margin slightly contracted medially; 
disk with concentric impressed lines. 
Locality. —San Buenaventura. 
Tapes Inezensis, PI. 7, fig. 1.—Less ventricose than the preceding, with a rounded base, 
and prominent concentric lines. 
Locality. —Santa Inez mountains. 
VENUS, Lin. 
Venus Pajaroana, PI. 4, figs. 1 and 2.—Obliquely ovate-obtuse, ventricose, very inequilateral; 
anterior margin obtusely rounded, posterior side sub-cuniform; posterior end truncated obliquely 
inwards. 
Locality. —Pajaro river, Santa Cruz. 
ARCOPAGIA, Brown. 
Arcopagia unda, PI. 4, figs. 3 and 4.—Sub triangular ; right valve profoundly ventricose ante¬ 
riorly ; profoundly sinuous posteriorly, or contracted from beak to beak; anterior end regularly 
and obtusely rounded; beaks nearly central; valves rugose-striate concentrically. 
Locality ._—Shore of Santa Barbara county, California. 
This species is described from one imperfect valve, which resembles A. biplicata, Con. It is 
somewhat larger than that species, has a much larger umbo, is less curved, being almost 
straight. In the same rock is a cast of a bivalve resembling a shell I have described under the 
name of Carditamon carinata. There is in the collection another cast of this shell in lime¬ 
stone, from Estrella. 
CYCLAS, Klein. LUCINA, Lam. 
Cyclas permacra, PI. 7, fig. 4.—Compressed, inequilateral; concentrically rugose-striate, 
striae distinct and acute. 
Locality. —Sierra Monica. 
The specimen described is imperfect. It somewhat resembles 0. panduta , Con., ( Lucina com- 
pressa, Lee,) but differs in having prominent lines. 
Cyclas estrellana, PI. 6, fig. 6.—Sub-oval, inequilaterally ventricose; valves extremely 
thick ; surface with concentric lines, probably mere lines of growth on the middle, but promi¬ 
nent and robust anteriorly. 
Locality. —Estrella. 
Length, 3£ inches. A broken cast, with a large portion of the shell of the left valve crys¬ 
tallized, and exhibiting a remarkable thickness over the umbo. 
ARCA, Lin. 
Arca obispoana, PL 5, fig. 1.—Oblong, or trapezoidal; very inequilateral, ventricose ; ribs 
about 26, little prominent, flattened ; sides rectangular with the back ; transversely rugose, 
or sub-crenulated. 
Locality. —San Luis Obispo valley, California. 
This species has been described from very perfect casts in an argillaceous gray marl. 
